Import Tycho weave client

35 files changed, 2602 insertions, 5123 deletions

diff --git a/services/sync/modules/FxaMigrator.jsm b/services/sync/modules/FxaMigrator.jsm
new file mode 100644
index 000000000..605ee5d7f
--- /dev/null
+++ b/services/sync/modules/FxaMigrator.jsm
@@ -0,0 +1,546 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict;"
+
+const {classes: Cc, interfaces: Ci, results: Cr, utils: Cu} = Components;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/Log.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/Task.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "fxAccounts",
+  "resource://gre/modules/FxAccounts.jsm");
+
+XPCOMUtils.defineLazyGetter(this, "WeaveService", function() {
+  return Cc["@mozilla.org/weave/service;1"]
+         .getService(Components.interfaces.nsISupports)
+         .wrappedJSObject;
+});
+
+XPCOMUtils.defineLazyModuleGetter(this, "Weave",
+  "resource://services-sync/main.js");
+
+// FxAccountsCommon.js doesn't use a "namespace", so create one here.
+let fxAccountsCommon = {};
+Cu.import("resource://gre/modules/FxAccountsCommon.js", fxAccountsCommon);
+
+// We send this notification whenever the "user" migration state changes.
+const OBSERVER_STATE_CHANGE_TOPIC = "fxa-migration:state-changed";
+// We also send the state notification when we *receive* this.  This allows
+// consumers to avoid loading this module until it receives a notification
+// from us (which may never happen if there's no migration to do)
+const OBSERVER_STATE_REQUEST_TOPIC = "fxa-migration:state-request";
+
+// We send this notification whenever the migration is paused waiting for
+// something internal to complete.
+const OBSERVER_INTERNAL_STATE_CHANGE_TOPIC = "fxa-migration:internal-state-changed";
+
+// We use this notification so Sync's healthreport module can record telemetry
+// (actually via "health report") for us.
+const OBSERVER_INTERNAL_TELEMETRY_TOPIC = "fxa-migration:internal-telemetry";
+
+const OBSERVER_TOPICS = [
+  "xpcom-shutdown",
+  "weave:service:sync:start",
+  "weave:service:sync:finish",
+  "weave:service:sync:error",
+  "weave:eol",
+  OBSERVER_STATE_REQUEST_TOPIC,
+  fxAccountsCommon.ONLOGIN_NOTIFICATION,
+  fxAccountsCommon.ONLOGOUT_NOTIFICATION,
+  fxAccountsCommon.ONVERIFIED_NOTIFICATION,
+];
+
+// A list of preference names we write to the migration sentinel.  We only
+// write ones that have a user-set value.
+const FXA_SENTINEL_PREFS = [
+  "identity.fxaccounts.auth.uri",
+  "identity.fxaccounts.remote.force_auth.uri",
+  "identity.fxaccounts.remote.signup.uri",
+  "identity.fxaccounts.remote.signin.uri",
+  "identity.fxaccounts.settings.uri",
+  "services.sync.tokenServerURI",
+];
+
+function Migrator() {
+  // Leave the log-level as Debug - Sync will setup log appenders such that
+  // these messages generally will not be seen unless other log related
+  // prefs are set.
+  this.log.level = Log.Level.Debug;
+
+  this._nextUserStatePromise = Promise.resolve();
+
+  for (let topic of OBSERVER_TOPICS) {
+    Services.obs.addObserver(this, topic, false);
+  }
+  // ._state is an optimization so we avoid sending redundant observer
+  // notifications when the state hasn't actually changed.
+  this._state = null;
+}
+
+Migrator.prototype = {
+  log: Log.repository.getLogger("Sync.SyncMigration"),
+
+  // What user action is necessary to push the migration forward?
+  // A |null| state means there is nothing to do.  Note that a null state implies
+  // either. (a) no migration is necessary or (b) that the migrator module is
+  // waiting for something outside of the user's control - eg, sync to complete,
+  // the migration sentinel to be uploaded, etc.  In most cases the wait will be
+  // short, but edge cases (eg, no network, sync bugs that prevent it stopping
+  // until shutdown) may require a significantly longer wait.
+  STATE_USER_FXA: "waiting for user to be signed in to FxA",
+  STATE_USER_FXA_VERIFIED: "waiting for a verified FxA user",
+
+  // What internal state are we at?  This is primarily used for FHR reporting so
+  // we can determine why exactly we might be stalled.
+  STATE_INTERNAL_WAITING_SYNC_COMPLETE: "waiting for sync to complete",
+  STATE_INTERNAL_WAITING_WRITE_SENTINEL: "waiting for sentinel to be written",
+  STATE_INTERNAL_WAITING_START_OVER: "waiting for sync to reset itself",
+  STATE_INTERNAL_COMPLETE: "migration complete",
+
+  // Flags for the telemetry we record.  The UI will call a helper to record
+  // the fact some UI was interacted with.
+  TELEMETRY_ACCEPTED: "accepted",
+  TELEMETRY_DECLINED: "declined",
+  TELEMETRY_UNLINKED: "unlinked",
+
+  finalize() {
+    for (let topic of OBSERVER_TOPICS) {
+      Services.obs.removeObserver(this, topic);
+    }
+  },
+
+  observe(subject, topic, data) {
+    this.log.debug("observed " + topic);
+    switch (topic) {
+      case "xpcom-shutdown":
+        this.finalize();
+        break;
+
+      case OBSERVER_STATE_REQUEST_TOPIC:
+        // someone has requested the state - send it.
+        this._queueCurrentUserState(true);
+        break;
+
+      default:
+        // some other observer that may affect our state has fired, so update.
+        this._queueCurrentUserState().then(
+          () => this.log.debug("update state from observer " + topic + " complete")
+        ).catch(err => {
+          let msg = "Failed to handle topic " + topic + ": " + err;
+          Cu.reportError(msg);
+          this.log.error(msg);
+        });
+    }
+  },
+
+  // Try and move to a state where we are blocked on a user action.
+  // This needs to be restartable, and the states may, in edge-cases, end
+  // up going backwards (eg, user logs out while we are waiting to be told
+  // about verification)
+  // This is called by our observer notifications - so if there is already
+  // a promise in-flight, it's possible we will miss something important - so
+  // we wait for the in-flight one to complete then fire another (ie, this
+  // is effectively a queue of promises)
+  _queueCurrentUserState(forceObserver = false) {
+    return this._nextUserStatePromise = this._nextUserStatePromise.then(
+      () => this._promiseCurrentUserState(forceObserver),
+      err => {
+        let msg = "Failed to determine the current user state: " + err;
+        Cu.reportError(msg);
+        this.log.error(msg);
+        return this._promiseCurrentUserState(forceObserver)
+      }
+    );
+  },
+
+  _promiseCurrentUserState: Task.async(function* (forceObserver) {
+    this.log.trace("starting _promiseCurrentUserState");
+    let update = (newState, email=null) => {
+      this.log.info("Migration state: '${state}' => '${newState}'",
+                    {state: this._state, newState: newState});
+      if (forceObserver || newState !== this._state) {
+        this._state = newState;
+        let subject = Cc["@mozilla.org/supports-string;1"]
+                      .createInstance(Ci.nsISupportsString);
+        subject.data = email || "";
+        Services.obs.notifyObservers(subject, OBSERVER_STATE_CHANGE_TOPIC, newState);
+      }
+      return newState;
+    }
+
+    // If we have no sync user, or are already using an FxA account we must
+    // be done.
+    if (WeaveService.fxAccountsEnabled) {
+      // should not be necessary, but if we somehow ended up with FxA enabled
+      // and sync blocked it would be bad - so better safe than sorry.
+      this.log.debug("FxA enabled - there's nothing to do!")
+      this._unblockSync();
+      return update(null);
+    }
+
+    // so we need to migrate - let's see how far along we are.
+    // If sync isn't in EOL mode, then we are still waiting for the server
+    // to offer the migration process - so no user action necessary.
+    let isEOL = false;
+    try {
+      isEOL = !!Services.prefs.getCharPref("services.sync.errorhandler.alert.mode");
+    } catch (e) {}
+
+    if (!isEOL) {
+      return update(null);
+    }
+
+    // So we are in EOL mode - have we a user?
+    let fxauser = yield fxAccounts.getSignedInUser();
+    if (!fxauser) {
+      // See if there is a migration sentinel so we can send the email
+      // address that was used on a different device for this account (ie, if
+      // this is a "join the party" migration rather than the first)
+      let sentinel = yield this._getSyncMigrationSentinel();
+      return update(this.STATE_USER_FXA, sentinel && sentinel.email);
+    }
+    if (!fxauser.verified) {
+      return update(this.STATE_USER_FXA_VERIFIED, fxauser.email);
+    }
+
+    // So we just have housekeeping to do - we aren't blocked on a user, so
+    // reflect that.
+    this.log.info("No next user state - doing some housekeeping");
+    update(null);
+
+    // We need to disable sync from automatically starting,
+    // and if we are currently syncing wait for it to complete.
+    this._blockSync();
+
+    // Are we currently syncing?
+    if (Weave.Service._locked) {
+      // our observers will kick us further along when complete.
+      this.log.info("waiting for sync to complete")
+      Services.obs.notifyObservers(null, OBSERVER_INTERNAL_STATE_CHANGE_TOPIC,
+                                   this.STATE_INTERNAL_WAITING_SYNC_COMPLETE);
+      return null;
+    }
+
+    // Write the migration sentinel if necessary.
+    Services.obs.notifyObservers(null, OBSERVER_INTERNAL_STATE_CHANGE_TOPIC,
+                                 this.STATE_INTERNAL_WAITING_WRITE_SENTINEL);
+    yield this._setMigrationSentinelIfNecessary();
+
+    // Get the list of enabled engines to we can restore that state.
+    let enginePrefs = this._getEngineEnabledPrefs();
+
+    // Must be ready to perform the actual migration.
+    this.log.info("Performing final sync migration steps");
+    // Do the actual migration.  We setup one observer for when the new identity
+    // is about to be initialized so we can reset some key preferences - but
+    // there's no promise associated with this.
+    let observeStartOverIdentity;
+    Services.obs.addObserver(observeStartOverIdentity = () => {
+      this.log.info("observed that startOver is about to re-initialize the identity");
+      Services.obs.removeObserver(observeStartOverIdentity, "weave:service:start-over:init-identity");
+      // We've now reset all sync prefs - set the engine related prefs back to
+      // what they were.
+      for (let [prefName, prefType, prefVal] of enginePrefs) {
+        this.log.debug("Restoring pref ${prefName} (type=${prefType}) to ${prefVal}",
+                       {prefName, prefType, prefVal});
+        switch (prefType) {
+          case Services.prefs.PREF_BOOL:
+            Services.prefs.setBoolPref(prefName, prefVal);
+            break;
+          case Services.prefs.PREF_STRING:
+            Services.prefs.setCharPref(prefName, prefVal);
+            break;
+          default:
+            // _getEngineEnabledPrefs doesn't return any other type...
+            Cu.reportError("unknown engine pref type for " + prefName + ": " + prefType);
+        }
+      }
+    }, "weave:service:start-over:init-identity", false);
+
+    // And another observer for the startOver being fully complete - the only
+    // reason for this is so we can wait until everything is fully reset.
+    let startOverComplete = new Promise((resolve, reject) => {
+      let observe;
+      Services.obs.addObserver(observe = () => {
+        this.log.info("observed that startOver is complete");
+        Services.obs.removeObserver(observe, "weave:service:start-over:finish");
+        resolve();
+      }, "weave:service:start-over:finish", false);
+    });
+
+    Weave.Service.startOver();
+    // need to wait for an observer.
+    Services.obs.notifyObservers(null, OBSERVER_INTERNAL_STATE_CHANGE_TOPIC,
+                                 this.STATE_INTERNAL_WAITING_START_OVER);
+    yield startOverComplete;
+    // observer fired, now kick things off with the FxA user.
+    this.log.info("scheduling initial FxA sync.");
+    // Note we technically don't need to unblockSync as by now all sync prefs
+    // have been reset - but it doesn't hurt.
+    this._unblockSync();
+    Weave.Service.scheduler.scheduleNextSync(0);
+
+    // Tell the front end that migration is now complete -- Sync is now
+    // configured with an FxA user.
+    forceObserver = true;
+    this.log.info("Migration complete");
+    update(null);
+
+    Services.obs.notifyObservers(null, OBSERVER_INTERNAL_STATE_CHANGE_TOPIC,
+                                 this.STATE_INTERNAL_COMPLETE);
+    return null;
+  }),
+
+  /* Return an object with the preferences we care about */
+  _getSentinelPrefs() {
+    let result = {};
+    for (let pref of FXA_SENTINEL_PREFS) {
+      if (Services.prefs.prefHasUserValue(pref)) {
+        result[pref] = Services.prefs.getCharPref(pref);
+      }
+    }
+    return result;
+  },
+
+  /* Apply any preferences we've obtained from the sentinel */
+  _applySentinelPrefs(savedPrefs) {
+    for (let pref of FXA_SENTINEL_PREFS) {
+      if (savedPrefs[pref]) {
+        Services.prefs.setCharPref(pref, savedPrefs[pref]);
+      }
+    }
+  },
+
+  /* Ask sync to upload the migration sentinel */
+  _setSyncMigrationSentinel: Task.async(function* () {
+    yield WeaveService.whenLoaded();
+    let signedInUser = yield fxAccounts.getSignedInUser();
+    let sentinel = {
+      email: signedInUser.email,
+      uid: signedInUser.uid,
+      verified: signedInUser.verified,
+      prefs: this._getSentinelPrefs(),
+    };
+    yield Weave.Service.setFxAMigrationSentinel(sentinel);
+  }),
+
+  /* Ask sync to upload the migration sentinal if we (or any other linked device)
+     haven't previously written one.
+   */
+  _setMigrationSentinelIfNecessary: Task.async(function* () {
+    if (!(yield this._getSyncMigrationSentinel())) {
+      this.log.info("writing the migration sentinel");
+      yield this._setSyncMigrationSentinel();
+    }
+  }),
+
+  /* Ask sync to return a migration sentinel if one exists, otherwise return null */
+  _getSyncMigrationSentinel: Task.async(function* () {
+    yield WeaveService.whenLoaded();
+    let sentinel = yield Weave.Service.getFxAMigrationSentinel();
+    this.log.debug("got migration sentinel ${}", sentinel);
+    return sentinel;
+  }),
+
+  _getDefaultAccountName: Task.async(function* (sentinel) {
+    // Requires looking to see if other devices have written a migration
+    // sentinel (eg, see _haveSynchedMigrationSentinel), and if not, see if
+    // the legacy account name appears to be a valid email address (via the
+    // services.sync.account pref), otherwise return null.
+    // NOTE: Sync does all this synchronously via nested event loops, but we
+    // expose a promise to make future migration to an async-sync easier.
+    if (sentinel && sentinel.email) {
+      this.log.info("defaultAccountName found via sentinel: ${}", sentinel.email);
+      return sentinel.email;
+    }
+    // No previous migrations, so check the existing account name.
+    let account = Weave.Service.identity.account;
+    if (account && account.contains("@")) {
+      this.log.info("defaultAccountName found via legacy account name: {}", account);
+      return account;
+    }
+    this.log.info("defaultAccountName could not find an account");
+    return null;
+  }),
+
+  // Prevent sync from automatically starting
+  _blockSync() {
+    Weave.Service.scheduler.blockSync();
+  },
+
+  _unblockSync() {
+    Weave.Service.scheduler.unblockSync();
+  },
+
+  /* Return a list of [prefName, prefType, prefVal] for all engine related
+     preferences.
+  */
+  _getEngineEnabledPrefs() {
+    let result = [];
+    for (let engine of Weave.Service.engineManager.getAll()) {
+      let prefName = "services.sync.engine." + engine.prefName;
+      let prefVal;
+      try {
+        prefVal = Services.prefs.getBoolPref(prefName);
+        result.push([prefName, Services.prefs.PREF_BOOL, prefVal]);
+      } catch (ex) {} /* just skip this pref */
+    }
+    // and the declined list.
+    try {
+      let prefName = "services.sync.declinedEngines";
+      let prefVal = Services.prefs.getCharPref(prefName);
+      result.push([prefName, Services.prefs.PREF_STRING, prefVal]);
+    } catch (ex) {}
+    return result;
+  },
+
+  /* return true if all engines are enabled, false otherwise. */
+  _allEnginesEnabled() {
+    return Weave.Service.engineManager.getAll().every(e => e.enabled);
+  },
+
+  /*
+   * Some helpers for the UI to try and move to the next state.
+   */
+
+  // Open a UI for the user to create a Firefox Account.  This should only be
+  // called while we are in the STATE_USER_FXA state.  When the user completes
+  // the creation we'll see an ONLOGIN_NOTIFICATION notification from FxA and
+  // we'll move to either the STATE_USER_FXA_VERIFIED state or we'll just
+  // complete the migration if they login as an already verified user.
+  createFxAccount: Task.async(function* (win) {
+    let {url, options} = yield this.getFxAccountCreationOptions();
+    win.switchToTabHavingURI(url, true, options);
+    // An FxA observer will fire when the user completes this, which will
+    // cause us to move to the next "user blocked" state and notify via our
+    // observer notification.
+  }),
+
+  // Returns an object with properties "url" and "options", suitable for
+  // opening FxAccounts to create/signin to FxA suitable for the migration
+  // state.  The caller of this is responsible for the actual opening of the
+  // page.
+  // This should only be called while we are in the STATE_USER_FXA state.  When
+  // the user completes the creation we'll see an ONLOGIN_NOTIFICATION
+  // notification from FxA and we'll move to either the STATE_USER_FXA_VERIFIED
+  // state or we'll just complete the migration if they login as an already
+  // verified user.
+  getFxAccountCreationOptions: Task.async(function* (win) {
+    // warn if we aren't in the expected state - but go ahead anyway!
+    if (this._state != this.STATE_USER_FXA) {
+      this.log.warn("getFxAccountCreationOptions called in an unexpected state: ${}", this._state);
+    }
+    // We need to obtain the sentinel and apply any prefs that might be
+    // specified *before* attempting to setup FxA as the prefs might
+    // specify custom servers etc.
+    let sentinel = yield this._getSyncMigrationSentinel();
+    if (sentinel && sentinel.prefs) {
+      this._applySentinelPrefs(sentinel.prefs);
+    }
+    // If we already have a sentinel then we assume the user has previously
+    // created the specified account, so just ask to sign-in.
+    let action = sentinel ? "signin" : "signup";
+    // See if we can find a default account name to use.
+    let email = yield this._getDefaultAccountName(sentinel);
+    let tail = email ? "&email=" + encodeURIComponent(email) : "";
+    // A special flag so server-side metrics can tell this is part of migration.
+    tail += "&migration=sync11";
+    // We want to ask FxA to offer a "Customize Sync" checkbox iff any engines
+    // are disabled.
+    let customize = !this._allEnginesEnabled();
+    tail += "&customizeSync=" + customize;
+
+    // We assume the caller of this is going to actually use it, so record
+    // telemetry now.
+    this.recordTelemetry(this.TELEMETRY_ACCEPTED);
+    return {
+      url: "about:accounts?action=" + action + tail,
+      options: {ignoreFragment: true, replaceQueryString: true}
+    };
+  }),
+
+  // Ask the FxA servers to re-send a verification mail for the currently
+  // logged in user. This should only be called while we are in the
+  // STATE_USER_FXA_VERIFIED state.  When the user clicks on the link in
+  // the mail we should see an ONVERIFIED_NOTIFICATION which will cause us
+  // to complete the migration.
+  resendVerificationMail: Task.async(function * (win) {
+    // warn if we aren't in the expected state - but go ahead anyway!
+    if (this._state != this.STATE_USER_FXA_VERIFIED) {
+      this.log.warn("resendVerificationMail called in an unexpected state: ${}", this._state);
+    }
+    let ok = true;
+    try {
+      yield fxAccounts.resendVerificationEmail();
+    } catch (ex) {
+      this.log.error("Failed to resend verification mail: ${}", ex);
+      ok = false;
+    }
+    this.recordTelemetry(this.TELEMETRY_ACCEPTED);
+    let fxauser = yield fxAccounts.getSignedInUser();
+    let sb = Services.strings.createBundle("chrome://browser/locale/accounts.properties");
+
+    let heading = ok ?
+                  sb.formatStringFromName("verificationSentHeading", [fxauser.email], 1) :
+                  sb.GetStringFromName("verificationNotSentHeading");
+    let title = sb.GetStringFromName(ok ? "verificationSentTitle" : "verificationNotSentTitle");
+    let description = sb.GetStringFromName(ok ? "verificationSentDescription"
+                                              : "verificationNotSentDescription");
+
+    let factory = Cc["@mozilla.org/prompter;1"]
+                    .getService(Ci.nsIPromptFactory);
+    let prompt = factory.getPrompt(win, Ci.nsIPrompt);
+    let bag = prompt.QueryInterface(Ci.nsIWritablePropertyBag2);
+    bag.setPropertyAsBool("allowTabModal", true);
+
+    prompt.alert(title, heading + "\n\n" + description);
+  }),
+
+  // "forget" about the current Firefox account. This should only be called
+  // while we are in the STATE_USER_FXA_VERIFIED state.  After this we will
+  // see an ONLOGOUT_NOTIFICATION, which will cause the migrator to return back
+  // to the STATE_USER_FXA state, from where they can choose a different account.
+  forgetFxAccount: Task.async(function * () {
+    // warn if we aren't in the expected state - but go ahead anyway!
+    if (this._state != this.STATE_USER_FXA_VERIFIED) {
+      this.log.warn("forgetFxAccount called in an unexpected state: ${}", this._state);
+    }
+    return fxAccounts.signOut();
+  }),
+
+  recordTelemetry(flag) {
+    // Note the value is the telemetry field name - but this is an
+    // implementation detail which could be changed later.
+    switch (flag) {
+      case this.TELEMETRY_ACCEPTED:
+      case this.TELEMETRY_UNLINKED:
+      case this.TELEMETRY_DECLINED:
+        Services.obs.notifyObservers(null, OBSERVER_INTERNAL_TELEMETRY_TOPIC, flag);
+        break;
+      default:
+        throw new Error("Unexpected telemetry flag: " + flag);
+    }
+  },
+
+  get learnMoreLink() {
+    try {
+      var url = Services.prefs.getCharPref("app.support.baseURL");
+    } catch (err) {
+      return null;
+    }
+    url += "sync-upgrade";
+    let sb = Services.strings.createBundle("chrome://weave/locale/services/sync.properties");
+    return {
+      text: sb.GetStringFromName("sync.eol.learnMore.label"),
+      href: Services.urlFormatter.formatURL(url),
+    };
+  },
+};
+
+// We expose a singleton
+this.EXPORTED_SYMBOLS = ["fxaMigrator"];
+let fxaMigrator = new Migrator();
diff --git a/services/sync/modules/SyncedTabs.jsm b/services/sync/modules/SyncedTabs.jsm
deleted file mode 100644
index 1a69e3564..000000000
--- a/services/sync/modules/SyncedTabs.jsm
+++ /dev/null
@@ -1,301 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-"use strict";
-
-this.EXPORTED_SYMBOLS = ["SyncedTabs"];
-
-
-const { classes: Cc, interfaces: Ci, results: Cr, utils: Cu } = Components;
-
-Cu.import("resource://gre/modules/Services.jsm");
-Cu.import("resource://gre/modules/XPCOMUtils.jsm");
-Cu.import("resource://gre/modules/Task.jsm");
-Cu.import("resource://gre/modules/Log.jsm");
-Cu.import("resource://gre/modules/PlacesUtils.jsm", this);
-Cu.import("resource://services-sync/main.js");
-Cu.import("resource://gre/modules/Preferences.jsm");
-
-// The Sync XPCOM service
-XPCOMUtils.defineLazyGetter(this, "weaveXPCService", function() {
-  return Cc["@mozilla.org/weave/service;1"]
-           .getService(Ci.nsISupports)
-           .wrappedJSObject;
-});
-
-// from MDN...
-function escapeRegExp(string) {
-  return string.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
-}
-
-// A topic we fire whenever we have new tabs available. This might be due
-// to a request made by this module to refresh the tab list, or as the result
-// of a regularly scheduled sync. The intent is that consumers just listen
-// for this notification and update their UI in response.
-const TOPIC_TABS_CHANGED = "services.sync.tabs.changed";
-
-// The interval, in seconds, before which we consider the existing list
-// of tabs "fresh enough" and don't force a new sync.
-const TABS_FRESH_ENOUGH_INTERVAL = 30;
-
-let log = Log.repository.getLogger("Sync.RemoteTabs");
-// A new scope to do the logging thang...
-(function() {
-  let level = Preferences.get("services.sync.log.logger.tabs");
-  if (level) {
-    let appender = new Log.DumpAppender();
-    log.level = appender.level = Log.Level[level] || Log.Level.Debug;
-    log.addAppender(appender);
-  }
-})();
-
-
-// A private singleton that does the work.
-let SyncedTabsInternal = {
-  /* Make a "tab" record. Returns a promise */
-  _makeTab: Task.async(function* (client, tab, url, showRemoteIcons) {
-    let icon;
-    if (showRemoteIcons) {
-      icon = tab.icon;
-    }
-    if (!icon) {
-      try {
-        icon = (yield PlacesUtils.promiseFaviconLinkUrl(url)).spec;
-      } catch (ex) { /* no favicon avaiable */ }
-    }
-    if (!icon) {
-      icon = "";
-    }
-    return {
-      type:  "tab",
-      title: tab.title || url,
-      url,
-      icon,
-      client: client.id,
-      lastUsed: tab.lastUsed,
-    };
-  }),
-
-  /* Make a "client" record. Returns a promise for consistency with _makeTab */
-  _makeClient: Task.async(function* (client) {
-    return {
-      id: client.id,
-      type: "client",
-      name: Weave.Service.clientsEngine.getClientName(client.id),
-      isMobile: Weave.Service.clientsEngine.isMobile(client.id),
-      lastModified: client.lastModified * 1000, // sec to ms
-      tabs: []
-    };
-  }),
-
-  _tabMatchesFilter(tab, filter) {
-    let reFilter = new RegExp(escapeRegExp(filter), "i");
-    return tab.url.match(reFilter) || tab.title.match(reFilter);
-  },
-
-  getTabClients: Task.async(function* (filter) {
-    log.info("Generating tab list with filter", filter);
-    let result = [];
-
-    // If Sync isn't ready, don't try and get anything.
-    if (!weaveXPCService.ready) {
-      log.debug("Sync isn't yet ready, so returning an empty tab list");
-      return result;
-    }
-
-    // A boolean that controls whether we should show the icon from the remote tab.
-    const showRemoteIcons = Preferences.get("services.sync.syncedTabs.showRemoteIcons", true);
-
-    let engine = Weave.Service.engineManager.get("tabs");
-
-    let seenURLs = new Set();
-    let parentIndex = 0;
-    let ntabs = 0;
-
-    for (let [guid, client] of Object.entries(engine.getAllClients())) {
-      if (!Weave.Service.clientsEngine.remoteClientExists(client.id)) {
-        continue;
-      }
-      let clientRepr = yield this._makeClient(client);
-      log.debug("Processing client", clientRepr);
-
-      for (let tab of client.tabs) {
-        let url = tab.urlHistory[0];
-        log.debug("remote tab", url);
-        // Note there are some issues with tracking "seen" tabs, including:
-        // * We really can't return the entire urlHistory record as we are
-        //   only checking the first entry - others might be different.
-        // * We don't update the |lastUsed| timestamp to reflect the
-        //   most-recently-seen time.
-        // In a followup we should consider simply dropping this |seenUrls|
-        // check and return duplicate records - it seems the user will be more
-        // confused by tabs not showing up on a device (because it was detected
-        // as a dupe so it only appears on a different device) than being
-        // confused by seeing the same tab on different clients.
-        if (!url || seenURLs.has(url)) {
-          continue;
-        }
-        let tabRepr = yield this._makeTab(client, tab, url, showRemoteIcons);
-        if (filter && !this._tabMatchesFilter(tabRepr, filter)) {
-          continue;
-        }
-        seenURLs.add(url);
-        clientRepr.tabs.push(tabRepr);
-      }
-      // We return all clients, even those without tabs - the consumer should
-      // filter it if they care.
-      ntabs += clientRepr.tabs.length;
-      result.push(clientRepr);
-    }
-    log.info(`Final tab list has ${result.length} clients with ${ntabs} tabs.`);
-    return result;
-  }),
-
-  syncTabs(force) {
-    if (!force) {
-      // Don't bother refetching tabs if we already did so recently
-      let lastFetch = Preferences.get("services.sync.lastTabFetch", 0);
-      let now = Math.floor(Date.now() / 1000);
-      if (now - lastFetch < TABS_FRESH_ENOUGH_INTERVAL) {
-        log.info("_refetchTabs was done recently, do not doing it again");
-        return Promise.resolve(false);
-      }
-    }
-
-    // If Sync isn't configured don't try and sync, else we will get reports
-    // of a login failure.
-    if (Weave.Status.checkSetup() == Weave.CLIENT_NOT_CONFIGURED) {
-      log.info("Sync client is not configured, so not attempting a tab sync");
-      return Promise.resolve(false);
-    }
-    // Ask Sync to just do the tabs engine if it can.
-    // Sync is currently synchronous, so do it after an event-loop spin to help
-    // keep the UI responsive.
-    return new Promise((resolve, reject) => {
-      Services.tm.currentThread.dispatch(() => {
-        try {
-          log.info("Doing a tab sync.");
-          Weave.Service.sync(["tabs"]);
-          resolve(true);
-        } catch (ex) {
-          log.error("Sync failed", ex);
-          reject(ex);
-        };
-      }, Ci.nsIThread.DISPATCH_NORMAL);
-    });
-  },
-
-  observe(subject, topic, data) {
-    log.trace(`observed topic=${topic}, data=${data}, subject=${subject}`);
-    switch (topic) {
-      case "weave:engine:sync:finish":
-        if (data != "tabs") {
-          return;
-        }
-        // The tabs engine just finished syncing
-        // Set our lastTabFetch pref here so it tracks both explicit sync calls
-        // and normally scheduled ones.
-        Preferences.set("services.sync.lastTabFetch", Math.floor(Date.now() / 1000));
-        Services.obs.notifyObservers(null, TOPIC_TABS_CHANGED, null);
-        break;
-      case "weave:service:start-over":
-        // start-over needs to notify so consumers find no tabs.
-        Preferences.reset("services.sync.lastTabFetch");
-        Services.obs.notifyObservers(null, TOPIC_TABS_CHANGED, null);
-        break;
-      case "nsPref:changed":
-        Services.obs.notifyObservers(null, TOPIC_TABS_CHANGED, null);
-        break;
-      default:
-        break;
-    }
-  },
-
-  // Returns true if Sync is configured to Sync tabs, false otherwise
-  get isConfiguredToSyncTabs() {
-    if (!weaveXPCService.ready) {
-      log.debug("Sync isn't yet ready; assuming tab engine is enabled");
-      return true;
-    }
-
-    let engine = Weave.Service.engineManager.get("tabs");
-    return engine && engine.enabled;
-  },
-
-  get hasSyncedThisSession() {
-    let engine = Weave.Service.engineManager.get("tabs");
-    return engine && engine.hasSyncedThisSession;
-  },
-};
-
-Services.obs.addObserver(SyncedTabsInternal, "weave:engine:sync:finish", false);
-Services.obs.addObserver(SyncedTabsInternal, "weave:service:start-over", false);
-// Observe the pref the indicates the state of the tabs engine has changed.
-// This will force consumers to re-evaluate the state of sync and update
-// accordingly.
-Services.prefs.addObserver("services.sync.engine.tabs", SyncedTabsInternal, false);
-
-// The public interface.
-this.SyncedTabs = {
-  // A mock-point for tests.
-  _internal: SyncedTabsInternal,
-
-  // We make the topic for the observer notification public.
-  TOPIC_TABS_CHANGED,
-
-  // Returns true if Sync is configured to Sync tabs, false otherwise
-  get isConfiguredToSyncTabs() {
-    return this._internal.isConfiguredToSyncTabs;
-  },
-
-  // Returns true if a tab sync has completed once this session. If this
-  // returns false, then getting back no clients/tabs possibly just means we
-  // are waiting for that first sync to complete.
-  get hasSyncedThisSession() {
-    return this._internal.hasSyncedThisSession;
-  },
-
-  // Return a promise that resolves with an array of client records, each with
-  // a .tabs array. Note that part of the contract for this module is that the
-  // returned objects are not shared between invocations, so callers are free
-  // to mutate the returned objects (eg, sort, truncate) however they see fit.
-  getTabClients(query) {
-    return this._internal.getTabClients(query);
-  },
-
-  // Starts a background request to start syncing tabs. Returns a promise that
-  // resolves when the sync is complete, but there's no resolved value -
-  // callers should be listening for TOPIC_TABS_CHANGED.
-  // If |force| is true we always sync. If false, we only sync if the most
-  // recent sync wasn't "recently".
-  syncTabs(force) {
-    return this._internal.syncTabs(force);
-  },
-
-  sortTabClientsByLastUsed(clients, maxTabs = Infinity) {
-    // First sort and filter the list of tabs for each client. Note that
-    // this module promises that the objects it returns are never
-    // shared, so we are free to mutate those objects directly.
-    for (let client of clients) {
-      let tabs = client.tabs;
-      tabs.sort((a, b) => b.lastUsed - a.lastUsed);
-      if (Number.isFinite(maxTabs)) {
-        client.tabs = tabs.slice(0, maxTabs);
-      }
-    }
-    // Now sort the clients - the clients are sorted in the order of the
-    // most recent tab for that client (ie, it is important the tabs for
-    // each client are already sorted.)
-    clients.sort((a, b) => {
-      if (a.tabs.length == 0) {
-        return 1; // b comes first.
-      }
-      if (b.tabs.length == 0) {
-        return -1; // a comes first.
-      }
-      return b.tabs[0].lastUsed - a.tabs[0].lastUsed;
-    });
-  },
-};
-
diff --git a/services/sync/modules/addonsreconciler.js b/services/sync/modules/addonsreconciler.js
index a60fc8d56..2e838e885 100644
--- a/services/sync/modules/addonsreconciler.js
+++ b/services/sync/modules/addonsreconciler.js
@@ -17,7 +17,7 @@
 
 "use strict";
 
-var Cu = Components.utils;
+const Cu = Components.utils;
 
 Cu.import("resource://gre/modules/Log.jsm");
 Cu.import("resource://services-sync/util.js");
@@ -218,12 +218,11 @@ AddonsReconciler.prototype = {
       }
 
       this._addons = json.addons;
-      for (let id in this._addons) {
-        let record = this._addons[id];
+      for each (let record in this._addons) {
         record.modified = new Date(record.modified);
       }
 
-      for (let [time, change, id] of json.changes) {
+      for each (let [time, change, id] in json.changes) {
         this._changes.push([new Date(time), change, id]);
       }
 
@@ -247,9 +246,9 @@ AddonsReconciler.prototype = {
     let file = path || DEFAULT_STATE_FILE;
     let state = {version: 1, addons: {}, changes: []};
 
-    for (let [id, record] of Object.entries(this._addons)) {
+    for (let [id, record] in Iterator(this._addons)) {
       state.addons[id] = {};
-      for (let [k, v] of Object.entries(record)) {
+      for (let [k, v] in Iterator(record)) {
         if (k == "modified") {
           state.addons[id][k] = v.getTime();
         }
@@ -259,7 +258,7 @@ AddonsReconciler.prototype = {
       }
     }
 
-    for (let [time, change, id] of this._changes) {
+    for each (let [time, change, id] in this._changes) {
       state.changes.push([time.getTime(), change, id]);
     }
 
@@ -351,14 +350,14 @@ AddonsReconciler.prototype = {
     AddonManager.getAllAddons(function (addons) {
       let ids = {};
 
-      for (let addon of addons) {
+      for each (let addon in addons) {
         ids[addon.id] = true;
         this.rectifyStateFromAddon(addon);
       }
 
       // Look for locally-defined add-ons that no longer exist and update their
       // record.
-      for (let [id, addon] of Object.entries(this._addons)) {
+      for (let [id, addon] in Iterator(this._addons)) {
         if (id in ids) {
           continue;
         }
@@ -374,7 +373,7 @@ AddonsReconciler.prototype = {
         }
 
         let installFound = false;
-        for (let install of installs) {
+        for each (let install in installs) {
           if (install.addon && install.addon.id == id &&
               install.state == AddonManager.STATE_INSTALLED) {
 
@@ -417,7 +416,7 @@ AddonsReconciler.prototype = {
    *        Addon instance being updated.
    */
   rectifyStateFromAddon: function rectifyStateFromAddon(addon) {
-    this._log.debug(`Rectifying state for addon ${addon.name} (version=${addon.version}, id=${addon.id})`);
+    this._log.debug("Rectifying state for addon: " + addon.id);
     this._ensureStateLoaded();
 
     let id = addon.id;
@@ -434,8 +433,7 @@ AddonsReconciler.prototype = {
         modified: now,
         type: addon.type,
         scope: addon.scope,
-        foreignInstall: addon.foreignInstall,
-        isSyncable: addon.isSyncable,
+        foreignInstall: addon.foreignInstall
       };
       this._addons[id] = record;
       this._log.debug("Adding change because add-on not present locally: " +
@@ -445,7 +443,6 @@ AddonsReconciler.prototype = {
     }
 
     let record = this._addons[id];
-    record.isSyncable = addon.isSyncable;
 
     if (!record.installed) {
       // It is possible the record is marked as uninstalled because an
@@ -486,11 +483,12 @@ AddonsReconciler.prototype = {
     this._log.info("Change recorded for " + state.id);
     this._changes.push([date, change, state.id]);
 
-    for (let listener of this._listeners) {
+    for each (let listener in this._listeners) {
       try {
         listener.changeListener.call(listener, date, change, state);
       } catch (ex) {
-        this._log.warn("Exception calling change listener", ex);
+        this._log.warn("Exception calling change listener: " +
+                       Utils.exceptionStr(ex));
       }
     }
   },
@@ -556,8 +554,7 @@ AddonsReconciler.prototype = {
    * @return Object on success on null on failure.
    */
   getAddonStateFromSyncGUID: function getAddonStateFromSyncGUID(guid) {
-    for (let id in this.addons) {
-      let addon = this.addons[id];
+    for each (let addon in this.addons) {
       if (addon.guid == guid) {
         return addon;
       }
@@ -636,7 +633,7 @@ AddonsReconciler.prototype = {
       }
     }
     catch (ex) {
-      this._log.warn("Exception", ex);
+      this._log.warn("Exception: " + Utils.exceptionStr(ex));
     }
   },
 
diff --git a/services/sync/modules/addonutils.js b/services/sync/modules/addonutils.js
index 95da6be0a..54b441b9e 100644
--- a/services/sync/modules/addonutils.js
+++ b/services/sync/modules/addonutils.js
@@ -6,7 +6,7 @@
 
 this.EXPORTED_SYMBOLS = ["AddonUtils"];
 
-var {interfaces: Ci, utils: Cu} = Components;
+const {interfaces: Ci, utils: Cu} = Components;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Log.jsm");
@@ -38,10 +38,21 @@ AddonUtilsInternal.prototype = {
    *        Function to be called with result of operation.
    */
   getInstallFromSearchResult:
-    function getInstallFromSearchResult(addon, cb) {
+    function getInstallFromSearchResult(addon, cb, requireSecureURI=true) {
 
     this._log.debug("Obtaining install for " + addon.id);
 
+    // Verify that the source URI uses TLS. We don't allow installs from
+    // insecure sources for security reasons. The Addon Manager ensures that
+    // cert validation, etc is performed.
+    if (requireSecureURI) {
+      let scheme = addon.sourceURI.scheme;
+      if (scheme != "https") {
+        cb(new Error("Insecure source URI scheme: " + scheme), addon.install);
+        return;
+      }
+    }
+
     // We should theoretically be able to obtain (and use) addon.install if
     // it is available. However, the addon.sourceURI rewriting won't be
     // reflected in the AddonInstall, so we can't use it. If we ever get rid
@@ -69,6 +80,8 @@ AddonUtilsInternal.prototype = {
    *   syncGUID - Sync GUID to use for the new add-on.
    *   enabled - Boolean indicating whether the add-on should be enabled upon
    *             install.
+   *   requireSecureURI - Boolean indicating whether to require a secure
+   *     URI to install from. This defaults to true.
    *
    * When complete it calls a callback with 2 arguments, error and result.
    *
@@ -92,6 +105,10 @@ AddonUtilsInternal.prototype = {
     function installAddonFromSearchResult(addon, options, cb) {
     this._log.info("Trying to install add-on from search result: " + addon.id);
 
+    if (options.requireSecureURI === undefined) {
+      options.requireSecureURI = true;
+    }
+
     this.getInstallFromSearchResult(addon, function onResult(error, install) {
       if (error) {
         cb(error, null);
@@ -147,10 +164,10 @@ AddonUtilsInternal.prototype = {
         install.install();
       }
       catch (ex) {
-        this._log.error("Error installing add-on", ex);
+        this._log.error("Error installing add-on: " + Utils.exceptionstr(ex));
         cb(ex, null);
       }
-    }.bind(this));
+    }.bind(this), options.requireSecureURI);
   },
 
   /**
@@ -231,7 +248,7 @@ AddonUtilsInternal.prototype = {
     }
 
     let ids = [];
-    for (let addon of installs) {
+    for each (let addon in installs) {
       ids.push(addon.id);
     }
 
@@ -244,7 +261,6 @@ AddonUtilsInternal.prototype = {
           installedIDs: [],
           installs:     [],
           addons:       [],
-          skipped:      [],
           errors:       []
         };
 
@@ -282,21 +298,15 @@ AddonUtilsInternal.prototype = {
         // server-side metrics aren't skewed (bug 708134). The server should
         // ideally send proper URLs, but this solution was deemed too
         // complicated at the time the functionality was implemented.
-        for (let addon of addons) {
-          // Find the specified options for this addon.
-          let options;
-          for (let install of installs) {
-            if (install.id == addon.id) {
-              options = install;
-              break;
-            }
-          }
-          if (!this.canInstallAddon(addon, options)) {
-            ourResult.skipped.push(addon.id);
+        for each (let addon in addons) {
+          // sourceURI presence isn't enforced by AddonRepository. So, we skip
+          // add-ons without a sourceURI.
+          if (!addon.sourceURI) {
+            this._log.info("Skipping install of add-on because missing " +
+                           "sourceURI: " + addon.id);
             continue;
           }
 
-          // We can go ahead and attempt to install it.
           toInstall.push(addon);
 
           // We should always be able to QI the nsIURI to nsIURL. If not, we
@@ -332,9 +342,9 @@ AddonUtilsInternal.prototype = {
 
         // Start all the installs asynchronously. They will report back to us
         // as they finish, eventually triggering the global callback.
-        for (let addon of toInstall) {
+        for each (let addon in toInstall) {
           let options = {};
-          for (let install of installs) {
+          for each (let install in installs) {
             if (install.id == addon.id) {
               options = install;
               break;
@@ -353,51 +363,9 @@ AddonUtilsInternal.prototype = {
   },
 
   /**
-   * Returns true if we are able to install the specified addon, false
-   * otherwise. It is expected that this will log the reason if it returns
-   * false.
-   *
-   * @param addon
-   *        (Addon) Add-on instance to check.
-   * @param options
-   *        (object) The options specified for this addon. See installAddons()
-   *        for the valid elements.
-   */
-  canInstallAddon(addon, options) {
-    // sourceURI presence isn't enforced by AddonRepository. So, we skip
-    // add-ons without a sourceURI.
-    if (!addon.sourceURI) {
-      this._log.info("Skipping install of add-on because missing " +
-                     "sourceURI: " + addon.id);
-      return false;
-    }
-    // Verify that the source URI uses TLS. We don't allow installs from
-    // insecure sources for security reasons. The Addon Manager ensures
-    // that cert validation etc is performed.
-    // (We should also consider just dropping this entirely and calling
-    // XPIProvider.isInstallAllowed, but that has additional semantics we might
-    // need to think through...)
-    let requireSecureURI = true;
-    if (options && options.requireSecureURI !== undefined) {
-      requireSecureURI = options.requireSecureURI;
-    }
-
-    if (requireSecureURI) {
-      let scheme = addon.sourceURI.scheme;
-      if (scheme != "https") {
-        this._log.info(`Skipping install of add-on "${addon.id}" because sourceURI's scheme of "${scheme}" is not trusted`);
-        return false;
-      }
-    }
-    this._log.info(`Add-on "${addon.id}" is able to be installed`);
-    return true;
-  },
-
-
-  /**
    * Update the user disabled flag for an add-on.
    *
-   * The supplied callback will be called when the operation is
+   * The supplied callback will ba called when the operation is
    * complete. If the new flag matches the existing or if the add-on
    * isn't currently active, the function will fire the callback
    * immediately. Else, the callback is invoked when the AddonManager
diff --git a/services/sync/modules/bookmark_validator.js b/services/sync/modules/bookmark_validator.js
deleted file mode 100644
index 2a94ba043..000000000
--- a/services/sync/modules/bookmark_validator.js
+++ /dev/null
@@ -1,784 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-"use strict";
-
-const Cu = Components.utils;
-
-Cu.import("resource://gre/modules/PlacesUtils.jsm");
-Cu.import("resource://gre/modules/PlacesSyncUtils.jsm");
-Cu.import("resource://gre/modules/Task.jsm");
-Cu.import("resource://gre/modules/XPCOMUtils.jsm");
-
-
-this.EXPORTED_SYMBOLS = ["BookmarkValidator", "BookmarkProblemData"];
-
-const LEFT_PANE_ROOT_ANNO = "PlacesOrganizer/OrganizerFolder";
-const LEFT_PANE_QUERY_ANNO = "PlacesOrganizer/OrganizerQuery";
-
-// Indicates if a local bookmark tree node should be excluded from syncing.
-function isNodeIgnored(treeNode) {
-  return treeNode.annos && treeNode.annos.some(anno => anno.name == LEFT_PANE_ROOT_ANNO ||
-                                                       anno.name == LEFT_PANE_QUERY_ANNO);
-}
-const BOOKMARK_VALIDATOR_VERSION = 1;
-
-/**
- * Result of bookmark validation. Contains the following fields which describe
- * server-side problems unless otherwise specified.
- *
- * - missingIDs (number): # of objects with missing ids
- * - duplicates (array of ids): ids seen more than once
- * - parentChildMismatches (array of {parent: parentid, child: childid}):
- *   instances where the child's parentid and the parent's children array
- *   do not match
- * - cycles (array of array of ids). List of cycles found in the server-side tree.
- * - clientCycles (array of array of ids). List of cycles found in the client-side tree.
- * - orphans (array of {id: string, parent: string}): List of nodes with
- *   either no parentid, or where the parent could not be found.
- * - missingChildren (array of {parent: id, child: id}):
- *   List of parent/children where the child id couldn't be found
- * - deletedChildren (array of { parent: id, child: id }):
- *   List of parent/children where child id was a deleted item (but still showed up
- *   in the children array)
- * - multipleParents (array of {child: id, parents: array of ids}):
- *   List of children that were part of multiple parent arrays
- * - deletedParents (array of ids) : List of records that aren't deleted but
- *   had deleted parents
- * - childrenOnNonFolder (array of ids): list of non-folders that still have
- *   children arrays
- * - duplicateChildren (array of ids): list of records who have the same
- *   child listed multiple times in their children array
- * - parentNotFolder (array of ids): list of records that have parents that
- *   aren't folders
- * - rootOnServer (boolean): true if the root came from the server
- * - badClientRoots (array of ids): Contains any client-side root ids where
- *   the root is missing or isn't a (direct) child of the places root.
- *
- * - clientMissing: Array of ids on the server missing from the client
- * - serverMissing: Array of ids on the client missing from the server
- * - serverDeleted: Array of ids on the client that the server had marked as deleted.
- * - serverUnexpected: Array of ids that appear on the server but shouldn't
- *   because the client attempts to never upload them.
- * - differences: Array of {id: string, differences: string array} recording
- *   the non-structural properties that are differente between the client and server
- * - structuralDifferences: As above, but contains the items where the differences were
- *   structural, that is, they contained childGUIDs or parentid
- */
-class BookmarkProblemData {
-  constructor() {
-    this.rootOnServer = false;
-    this.missingIDs = 0;
-
-    this.duplicates = [];
-    this.parentChildMismatches = [];
-    this.cycles = [];
-    this.clientCycles = [];
-    this.orphans = [];
-    this.missingChildren = [];
-    this.deletedChildren = [];
-    this.multipleParents = [];
-    this.deletedParents = [];
-    this.childrenOnNonFolder = [];
-    this.duplicateChildren = [];
-    this.parentNotFolder = [];
-
-    this.badClientRoots = [];
-    this.clientMissing = [];
-    this.serverMissing = [];
-    this.serverDeleted = [];
-    this.serverUnexpected = [];
-    this.differences = [];
-    this.structuralDifferences = [];
-  }
-
-  /**
-   * Convert ("difference", [{ differences: ["tags", "name"] }, { differences: ["name"] }]) into
-   * [{ name: "difference:tags", count: 1}, { name: "difference:name", count: 2 }], etc.
-   */
-  _summarizeDifferences(prefix, diffs) {
-    let diffCounts = new Map();
-    for (let { differences } of diffs) {
-      for (let type of differences) {
-        let name = prefix + ":" + type;
-        let count = diffCounts.get(name) || 0;
-        diffCounts.set(name, count + 1);
-      }
-    }
-    return [...diffCounts].map(([name, count]) => ({ name, count }));
-  }
-
-  /**
-   * Produce a list summarizing problems found. Each entry contains {name, count},
-   * where name is the field name for the problem, and count is the number of times
-   * the problem was encountered.
-   *
-   * Validation has failed if all counts are not 0.
-   *
-   * If the `full` argument is truthy, we also include information about which
-   * properties we saw structural differences in. Currently, this means either
-   * "sdiff:parentid" and "sdiff:childGUIDS" may be present.
-   */
-  getSummary(full) {
-    let result = [
-      { name: "clientMissing", count: this.clientMissing.length },
-      { name: "serverMissing", count: this.serverMissing.length },
-      { name: "serverDeleted", count: this.serverDeleted.length },
-      { name: "serverUnexpected", count: this.serverUnexpected.length },
-
-      { name: "structuralDifferences", count: this.structuralDifferences.length },
-      { name: "differences", count: this.differences.length },
-
-      { name: "missingIDs", count: this.missingIDs },
-      { name: "rootOnServer", count: this.rootOnServer ? 1 : 0 },
-
-      { name: "duplicates", count: this.duplicates.length },
-      { name: "parentChildMismatches", count: this.parentChildMismatches.length },
-      { name: "cycles", count: this.cycles.length },
-      { name: "clientCycles", count: this.clientCycles.length },
-      { name: "badClientRoots", count: this.badClientRoots.length },
-      { name: "orphans", count: this.orphans.length },
-      { name: "missingChildren", count: this.missingChildren.length },
-      { name: "deletedChildren", count: this.deletedChildren.length },
-      { name: "multipleParents", count: this.multipleParents.length },
-      { name: "deletedParents", count: this.deletedParents.length },
-      { name: "childrenOnNonFolder", count: this.childrenOnNonFolder.length },
-      { name: "duplicateChildren", count: this.duplicateChildren.length },
-      { name: "parentNotFolder", count: this.parentNotFolder.length },
-    ];
-    if (full) {
-      let structural = this._summarizeDifferences("sdiff", this.structuralDifferences);
-      result.push.apply(result, structural);
-    }
-    return result;
-  }
-}
-
-// Defined lazily to avoid initializing PlacesUtils.bookmarks too soon.
-XPCOMUtils.defineLazyGetter(this, "SYNCED_ROOTS", () => [
-  PlacesUtils.bookmarks.menuGuid,
-  PlacesUtils.bookmarks.toolbarGuid,
-  PlacesUtils.bookmarks.unfiledGuid,
-  PlacesUtils.bookmarks.mobileGuid,
-]);
-
-class BookmarkValidator {
-
-  _followQueries(recordMap) {
-    for (let [guid, entry] of recordMap) {
-      if (entry.type !== "query" && (!entry.bmkUri || !entry.bmkUri.startsWith("place:"))) {
-        continue;
-      }
-      // Might be worth trying to parse the place: query instead so that this
-      // works "automatically" with things like aboutsync.
-      let queryNodeParent = PlacesUtils.getFolderContents(entry, false, true);
-      if (!queryNodeParent || !queryNodeParent.root.hasChildren) {
-        continue;
-      }
-      queryNodeParent = queryNodeParent.root;
-      let queryNode = null;
-      let numSiblings = 0;
-      let containerWasOpen = queryNodeParent.containerOpen;
-      queryNodeParent.containerOpen = true;
-      try {
-        try {
-          numSiblings = queryNodeParent.childCount;
-        } catch (e) {
-          // This throws when we can't actually get the children. This is the
-          // case for history containers, tag queries, ...
-          continue;
-        }
-        for (let i = 0; i < numSiblings && !queryNode; ++i) {
-          let child = queryNodeParent.getChild(i);
-          if (child && child.bookmarkGuid && child.bookmarkGuid === guid) {
-            queryNode = child;
-          }
-        }
-      } finally {
-        queryNodeParent.containerOpen = containerWasOpen;
-      }
-      if (!queryNode) {
-        continue;
-      }
-
-      let concreteId = PlacesUtils.getConcreteItemGuid(queryNode);
-      if (!concreteId) {
-        continue;
-      }
-      let concreteItem = recordMap.get(concreteId);
-      if (!concreteItem) {
-        continue;
-      }
-      entry.concrete = concreteItem;
-    }
-  }
-
-  createClientRecordsFromTree(clientTree) {
-    // Iterate over the treeNode, converting it to something more similar to what
-    // the server stores.
-    let records = [];
-    let recordsByGuid = new Map();
-    let syncedRoots = SYNCED_ROOTS;
-    function traverse(treeNode, synced) {
-      if (!synced) {
-        synced = syncedRoots.includes(treeNode.guid);
-      } else if (isNodeIgnored(treeNode)) {
-        synced = false;
-      }
-      let guid = PlacesSyncUtils.bookmarks.guidToSyncId(treeNode.guid);
-      let itemType = 'item';
-      treeNode.ignored = !synced;
-      treeNode.id = guid;
-      switch (treeNode.type) {
-        case PlacesUtils.TYPE_X_MOZ_PLACE:
-          let query = null;
-          if (treeNode.annos && treeNode.uri.startsWith("place:")) {
-            query = treeNode.annos.find(({name}) =>
-              name === PlacesSyncUtils.bookmarks.SMART_BOOKMARKS_ANNO);
-          }
-          if (query && query.value) {
-            itemType = 'query';
-          } else {
-            itemType = 'bookmark';
-          }
-          break;
-        case PlacesUtils.TYPE_X_MOZ_PLACE_CONTAINER:
-          let isLivemark = false;
-          if (treeNode.annos) {
-            for (let anno of treeNode.annos) {
-              if (anno.name === PlacesUtils.LMANNO_FEEDURI) {
-                isLivemark = true;
-                treeNode.feedUri = anno.value;
-              } else if (anno.name === PlacesUtils.LMANNO_SITEURI) {
-                isLivemark = true;
-                treeNode.siteUri = anno.value;
-              }
-            }
-          }
-          itemType = isLivemark ? "livemark" : "folder";
-          break;
-        case PlacesUtils.TYPE_X_MOZ_PLACE_SEPARATOR:
-          itemType = 'separator';
-          break;
-      }
-
-      if (treeNode.tags) {
-        treeNode.tags = treeNode.tags.split(",");
-      } else {
-        treeNode.tags = [];
-      }
-      treeNode.type = itemType;
-      treeNode.pos = treeNode.index;
-      treeNode.bmkUri = treeNode.uri;
-      records.push(treeNode);
-      // We want to use the "real" guid here.
-      recordsByGuid.set(treeNode.guid, treeNode);
-      if (treeNode.type === 'folder') {
-        treeNode.childGUIDs = [];
-        if (!treeNode.children) {
-          treeNode.children = [];
-        }
-        for (let child of treeNode.children) {
-          traverse(child, synced);
-          child.parent = treeNode;
-          child.parentid = guid;
-          treeNode.childGUIDs.push(child.guid);
-        }
-      }
-    }
-    traverse(clientTree, false);
-    clientTree.id = 'places';
-    this._followQueries(recordsByGuid);
-    return records;
-  }
-
-  /**
-   * Process the server-side list. Mainly this builds the records into a tree,
-   * but it also records information about problems, and produces arrays of the
-   * deleted and non-deleted nodes.
-   *
-   * Returns an object containing:
-   * - records:Array of non-deleted records. Each record contains the following
-   *    properties
-   *     - childGUIDs (array of strings, only present if type is 'folder'): the
-   *       list of child GUIDs stored on the server.
-   *     - children (array of records, only present if type is 'folder'):
-   *       each record has these same properties. This may differ in content
-   *       from what you may expect from the childGUIDs list, as it won't
-   *       contain any records that could not be found.
-   *     - parent (record): The parent to this record.
-   *     - Unchanged properties send down from the server: id, title, type,
-   *       parentName, parentid, bmkURI, keyword, tags, pos, queryId, loadInSidebar
-   * - root: Root of the server-side bookmark tree. Has the same properties as
-   *   above.
-   * - deletedRecords: As above, but only contains items that the server sent
-   *   where it also sent indication that the item should be deleted.
-   * - problemData: a BookmarkProblemData object, with the caveat that
-   *   the fields describing client/server relationship will not have been filled
-   *   out yet.
-   */
-  inspectServerRecords(serverRecords) {
-    let deletedItemIds = new Set();
-    let idToRecord = new Map();
-    let deletedRecords = [];
-
-    let folders = [];
-    let problems = [];
-
-    let problemData = new BookmarkProblemData();
-
-    let resultRecords = [];
-
-    for (let record of serverRecords) {
-      if (!record.id) {
-        ++problemData.missingIDs;
-        continue;
-      }
-      if (record.deleted) {
-        deletedItemIds.add(record.id);
-      } else {
-        if (idToRecord.has(record.id)) {
-          problemData.duplicates.push(record.id);
-          continue;
-        }
-      }
-      idToRecord.set(record.id, record);
-
-      if (record.children) {
-        if (record.type !== "folder") {
-          // Due to implementation details in engines/bookmarks.js, (Livemark
-          // subclassing BookmarkFolder) Livemarks will have a children array,
-          // but it should still be empty.
-          if (!record.children.length) {
-            continue;
-          }
-          // Otherwise we mark it as an error and still try to resolve the children
-          problemData.childrenOnNonFolder.push(record.id);
-        }
-        folders.push(record);
-
-        if (new Set(record.children).size !== record.children.length) {
-          problemData.duplicateChildren.push(record.id)
-        }
-
-        // The children array stores special guids as their local guid values,
-        // e.g. 'menu________' instead of 'menu', but all other parts of the
-        // serverside bookmark info stores it as the special value ('menu').
-        record.childGUIDs = record.children;
-        record.children = record.children.map(childID => {
-          return PlacesSyncUtils.bookmarks.guidToSyncId(childID);
-        });
-      }
-    }
-
-    for (let deletedId of deletedItemIds) {
-      let record = idToRecord.get(deletedId);
-      if (record && !record.isDeleted) {
-        deletedRecords.push(record);
-        record.isDeleted = true;
-      }
-    }
-
-    let root = idToRecord.get('places');
-
-    if (!root) {
-      // Fabricate a root. We want to remember that it's fake so that we can
-      // avoid complaining about stuff like it missing it's childGUIDs later.
-      root = { id: 'places', children: [], type: 'folder', title: '', fake: true };
-      resultRecords.push(root);
-      idToRecord.set('places', root);
-    } else {
-      problemData.rootOnServer = true;
-    }
-
-    // Build the tree, find orphans, and record most problems having to do with
-    // the tree structure.
-    for (let [id, record] of idToRecord) {
-      if (record === root) {
-        continue;
-      }
-
-      if (record.isDeleted) {
-        continue;
-      }
-
-      let parentID = record.parentid;
-      if (!parentID) {
-        problemData.orphans.push({id: record.id, parent: parentID});
-        continue;
-      }
-
-      let parent = idToRecord.get(parentID);
-      if (!parent) {
-        problemData.orphans.push({id: record.id, parent: parentID});
-        continue;
-      }
-
-      if (parent.type !== 'folder') {
-        problemData.parentNotFolder.push(record.id);
-        if (!parent.children) {
-          parent.children = [];
-        }
-        if (!parent.childGUIDs) {
-          parent.childGUIDs = [];
-        }
-      }
-
-      if (!record.isDeleted) {
-        resultRecords.push(record);
-      }
-
-      record.parent = parent;
-      if (parent !== root || problemData.rootOnServer) {
-        let childIndex = parent.children.indexOf(id);
-        if (childIndex < 0) {
-          problemData.parentChildMismatches.push({parent: parent.id, child: record.id});
-        } else {
-          parent.children[childIndex] = record;
-        }
-      } else {
-        parent.children.push(record);
-      }
-
-      if (parent.isDeleted && !record.isDeleted) {
-        problemData.deletedParents.push(record.id);
-      }
-
-      // We used to check if the parentName on the server matches the actual
-      // local parent name, but given this is used only for de-duping a record
-      // the first time it is seen and expensive to keep up-to-date, we decided
-      // to just stop recording it. See bug 1276969 for more.
-    }
-
-    // Check that we aren't missing any children.
-    for (let folder of folders) {
-      folder.unfilteredChildren = folder.children;
-      folder.children = [];
-      for (let ci = 0; ci < folder.unfilteredChildren.length; ++ci) {
-        let child = folder.unfilteredChildren[ci];
-        let childObject;
-        if (typeof child == "string") {
-          // This can happen the parent refers to a child that has a different
-          // parentid, or if it refers to a missing or deleted child. It shouldn't
-          // be possible with totally valid bookmarks.
-          childObject = idToRecord.get(child);
-          if (!childObject) {
-            problemData.missingChildren.push({parent: folder.id, child});
-          } else {
-            folder.unfilteredChildren[ci] = childObject;
-            if (childObject.isDeleted) {
-              problemData.deletedChildren.push({ parent: folder.id, child });
-            }
-          }
-        } else {
-          childObject = child;
-        }
-
-        if (!childObject) {
-          continue;
-        }
-
-        if (childObject.parentid === folder.id) {
-          folder.children.push(childObject);
-          continue;
-        }
-
-        // The child is very probably in multiple `children` arrays --
-        // see if we already have a problem record about it.
-        let currentProblemRecord = problemData.multipleParents.find(pr =>
-          pr.child === child);
-
-        if (currentProblemRecord) {
-          currentProblemRecord.parents.push(folder.id);
-          continue;
-        }
-
-        let otherParent = idToRecord.get(childObject.parentid);
-        // it's really an ... orphan ... sort of.
-        if (!otherParent) {
-          // if we never end up adding to this parent's list, we filter it out after this loop.
-          problemData.multipleParents.push({
-            child,
-            parents: [folder.id]
-          });
-          if (!problemData.orphans.some(r => r.id === child)) {
-            problemData.orphans.push({
-              id: child,
-              parent: childObject.parentid
-            });
-          }
-          continue;
-        }
-
-        if (otherParent.isDeleted) {
-          if (!problemData.deletedParents.includes(child)) {
-            problemData.deletedParents.push(child);
-          }
-          continue;
-        }
-
-        if (otherParent.childGUIDs && !otherParent.childGUIDs.includes(child)) {
-          if (!problemData.parentChildMismatches.some(r => r.child === child)) {
-            // Might not be possible to get here.
-            problemData.parentChildMismatches.push({ child, parent: folder.id });
-          }
-        }
-
-        problemData.multipleParents.push({
-          child,
-          parents: [childObject.parentid, folder.id]
-        });
-      }
-    }
-    problemData.multipleParents = problemData.multipleParents.filter(record =>
-      record.parents.length >= 2);
-
-    problemData.cycles = this._detectCycles(resultRecords);
-
-    return {
-      deletedRecords,
-      records: resultRecords,
-      problemData,
-      root,
-    };
-  }
-
-  // helper for inspectServerRecords
-  _detectCycles(records) {
-    // currentPath and pathLookup contain the same data. pathLookup is faster to
-    // query, but currentPath gives is the order of traversal that we need in
-    // order to report the members of the cycles.
-    let pathLookup = new Set();
-    let currentPath = [];
-    let cycles = [];
-    let seenEver = new Set();
-    const traverse = node => {
-      if (pathLookup.has(node)) {
-        let cycleStart = currentPath.lastIndexOf(node);
-        let cyclePath = currentPath.slice(cycleStart).map(n => n.id);
-        cycles.push(cyclePath);
-        return;
-      } else if (seenEver.has(node)) {
-        // If we're checking the server, this is a problem, but it should already be reported.
-        // On the client, this could happen due to including `node.concrete` in the child list.
-        return;
-      }
-      seenEver.add(node);
-      let children = node.children || [];
-      if (node.concrete) {
-        children.push(node.concrete);
-      }
-      if (children) {
-        pathLookup.add(node);
-        currentPath.push(node);
-        for (let child of children) {
-          traverse(child);
-        }
-        currentPath.pop();
-        pathLookup.delete(node);
-      }
-    };
-    for (let record of records) {
-      if (!seenEver.has(record)) {
-        traverse(record);
-      }
-    }
-
-    return cycles;
-  }
-
-  // Perform client-side sanity checking that doesn't involve server data
-  _validateClient(problemData, clientRecords) {
-    problemData.clientCycles = this._detectCycles(clientRecords);
-    for (let rootGUID of SYNCED_ROOTS) {
-      let record = clientRecords.find(record =>
-        record.guid === rootGUID);
-      if (!record || record.parentid !== "places") {
-        problemData.badClientRoots.push(rootGUID);
-      }
-    }
-  }
-
-  /**
-   * Compare the list of server records with the client tree.
-   *
-   * Returns the same data as described in the inspectServerRecords comment,
-   * with the following additional fields.
-   * - clientRecords: an array of client records in a similar format to
-   *   the .records (ie, server records) entry.
-   * - problemData is the same as for inspectServerRecords, except all properties
-   *   will be filled out.
-   */
-  compareServerWithClient(serverRecords, clientTree) {
-
-    let clientRecords = this.createClientRecordsFromTree(clientTree);
-    let inspectionInfo = this.inspectServerRecords(serverRecords);
-    inspectionInfo.clientRecords = clientRecords;
-
-    // Mainly do this to remove deleted items and normalize child guids.
-    serverRecords = inspectionInfo.records;
-    let problemData = inspectionInfo.problemData;
-
-    this._validateClient(problemData, clientRecords);
-
-    let matches = [];
-
-    let allRecords = new Map();
-    let serverDeletedLookup = new Set(inspectionInfo.deletedRecords.map(r => r.id));
-
-    for (let sr of serverRecords) {
-      if (sr.fake) {
-        continue;
-      }
-      allRecords.set(sr.id, {client: null, server: sr});
-    }
-
-    for (let cr of clientRecords) {
-      let unified = allRecords.get(cr.id);
-      if (!unified) {
-        allRecords.set(cr.id, {client: cr, server: null});
-      } else {
-        unified.client = cr;
-      }
-    }
-
-
-    for (let [id, {client, server}] of allRecords) {
-      if (!client && server) {
-        problemData.clientMissing.push(id);
-        continue;
-      }
-      if (!server && client) {
-        if (serverDeletedLookup.has(id)) {
-          problemData.serverDeleted.push(id);
-        } else if (!client.ignored && client.id != "places") {
-          problemData.serverMissing.push(id);
-        }
-        continue;
-      }
-      if (server && client && client.ignored) {
-        problemData.serverUnexpected.push(id);
-      }
-      let differences = [];
-      let structuralDifferences = [];
-
-      // Don't bother comparing titles of roots. It's okay if locally it's
-      // "Mobile Bookmarks", but the server thinks it's "mobile".
-      // TODO: We probably should be handing other localized bookmarks (e.g.
-      // default bookmarks) here as well, see bug 1316041.
-      if (!SYNCED_ROOTS.includes(client.guid)) {
-        // We want to treat undefined, null and an empty string as identical
-        if ((client.title || "") !== (server.title || "")) {
-          differences.push("title");
-        }
-      }
-
-      if (client.parentid || server.parentid) {
-        if (client.parentid !== server.parentid) {
-          structuralDifferences.push('parentid');
-        }
-      }
-
-      if (client.tags || server.tags) {
-        let cl = client.tags || [];
-        let sl = server.tags || [];
-        if (cl.length !== sl.length || !cl.every((tag, i) => sl.indexOf(tag) >= 0)) {
-          differences.push('tags');
-        }
-      }
-
-      let sameType = client.type === server.type;
-      if (!sameType) {
-        if (server.type === "query" && client.type === "bookmark" && client.bmkUri.startsWith("place:")) {
-          sameType = true;
-        }
-      }
-
-
-      if (!sameType) {
-        differences.push('type');
-      } else {
-        switch (server.type) {
-          case 'bookmark':
-          case 'query':
-            if (server.bmkUri !== client.bmkUri) {
-              differences.push('bmkUri');
-            }
-            break;
-          case "livemark":
-            if (server.feedUri != client.feedUri) {
-              differences.push("feedUri");
-            }
-            if (server.siteUri != client.siteUri) {
-              differences.push("siteUri");
-            }
-            break;
-          case 'folder':
-            if (server.id === 'places' && !problemData.rootOnServer) {
-              // It's the fabricated places root. It won't have the GUIDs, but
-              // it doesn't matter.
-              break;
-            }
-            if (client.childGUIDs || server.childGUIDs) {
-              let cl = client.childGUIDs || [];
-              let sl = server.childGUIDs || [];
-              if (cl.length !== sl.length || !cl.every((id, i) => sl[i] === id)) {
-                structuralDifferences.push('childGUIDs');
-              }
-            }
-            break;
-        }
-      }
-
-      if (differences.length) {
-        problemData.differences.push({id, differences});
-      }
-      if (structuralDifferences.length) {
-        problemData.structuralDifferences.push({ id, differences: structuralDifferences });
-      }
-    }
-    return inspectionInfo;
-  }
-
-  _getServerState(engine) {
-    let collection = engine.itemSource();
-    let collectionKey = engine.service.collectionKeys.keyForCollection(engine.name);
-    collection.full = true;
-    let items = [];
-    collection.recordHandler = function(item) {
-      item.decrypt(collectionKey);
-      items.push(item.cleartext);
-    };
-    let resp = collection.getBatched();
-    if (!resp.success) {
-      throw resp;
-    }
-    return items;
-  }
-
-  validate(engine) {
-    let self = this;
-    return Task.spawn(function*() {
-      let start = Date.now();
-      let clientTree = yield PlacesUtils.promiseBookmarksTree("", {
-        includeItemIds: true
-      });
-      let serverState = self._getServerState(engine);
-      let serverRecordCount = serverState.length;
-      let result = self.compareServerWithClient(serverState, clientTree);
-      let end = Date.now();
-      let duration = end-start;
-      return {
-        duration,
-        version: self.version,
-        problems: result.problemData,
-        recordCount: serverRecordCount
-      };
-    });
-  }
-
-};
-
-BookmarkValidator.prototype.version = BOOKMARK_VALIDATOR_VERSION;
-
diff --git a/services/sync/modules/browserid_identity.js b/services/sync/modules/browserid_identity.js
index db3821518..bc8ea6b30 100644
--- a/services/sync/modules/browserid_identity.js
+++ b/services/sync/modules/browserid_identity.js
@@ -4,9 +4,9 @@
 
 "use strict";
 
-this.EXPORTED_SYMBOLS = ["BrowserIDManager", "AuthenticationError"];
+this.EXPORTED_SYMBOLS = ["BrowserIDManager"];
 
-var {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
 
 Cu.import("resource://gre/modules/Log.jsm");
 Cu.import("resource://services-common/async.js");
@@ -39,13 +39,12 @@ XPCOMUtils.defineLazyGetter(this, 'log', function() {
 });
 
 // FxAccountsCommon.js doesn't use a "namespace", so create one here.
-var fxAccountsCommon = {};
+let fxAccountsCommon = {};
 Cu.import("resource://gre/modules/FxAccountsCommon.js", fxAccountsCommon);
 
 const OBSERVER_TOPICS = [
   fxAccountsCommon.ONLOGIN_NOTIFICATION,
   fxAccountsCommon.ONLOGOUT_NOTIFICATION,
-  fxAccountsCommon.ON_ACCOUNT_STATE_CHANGE_NOTIFICATION,
 ];
 
 const PREF_SYNC_SHOW_CUSTOMIZATION = "services.sync-setup.ui.showCustomizationDialog";
@@ -66,9 +65,8 @@ function deriveKeyBundle(kB) {
   some other error object (which should do the right thing when toString() is
   called on it)
 */
-function AuthenticationError(details, source) {
+function AuthenticationError(details) {
   this.details = details;
-  this.source = source;
 }
 
 AuthenticationError.prototype = {
@@ -106,6 +104,12 @@ this.BrowserIDManager.prototype = {
   // we don't consider the lack of a keybundle as a failure state.
   _shouldHaveSyncKeyBundle: false,
 
+  get readyToAuthenticate() {
+    // We are finished initializing when we *should* have a sync key bundle,
+    // although we might not actually have one due to auth failures etc.
+    return this._shouldHaveSyncKeyBundle;
+  },
+
   get needsCustomization() {
     try {
       return Services.prefs.getBoolPref(PREF_SYNC_SHOW_CUSTOMIZATION);
@@ -114,34 +118,11 @@ this.BrowserIDManager.prototype = {
     }
   },
 
-  hashedUID() {
-    if (!this._token) {
-      throw new Error("hashedUID: Don't have token");
-    }
-    return this._token.hashed_fxa_uid
-  },
-
-  deviceID() {
-    return this._signedInUser && this._signedInUser.deviceId;
-  },
-
   initialize: function() {
     for (let topic of OBSERVER_TOPICS) {
       Services.obs.addObserver(this, topic, false);
     }
-    // and a background fetch of account data just so we can set this.account,
-    // so we have a username available before we've actually done a login.
-    // XXX - this is actually a hack just for tests and really shouldn't be
-    // necessary. Also, you'd think it would be safe to allow this.account to
-    // be set to null when there's no user logged in, but argue with the test
-    // suite, not with me :)
-    this._fxaService.getSignedInUser().then(accountData => {
-      if (accountData) {
-        this.account = accountData.email;
-      }
-    }).catch(err => {
-      // As above, this is only for tests so it is safe to ignore.
-    });
+    return this.initializeWithCurrentIdentity();
   },
 
   /**
@@ -149,7 +130,7 @@ this.BrowserIDManager.prototype = {
    * the user is logged in, or is rejected if the login attempt has failed.
    */
   ensureLoggedIn: function() {
-    if (!this._shouldHaveSyncKeyBundle && this.whenReadyToAuthenticate) {
+    if (!this._shouldHaveSyncKeyBundle) {
       // We are already in the process of logging in.
       return this.whenReadyToAuthenticate.promise;
     }
@@ -163,7 +144,7 @@ this.BrowserIDManager.prototype = {
     // re-entering of credentials by the user is necessary we don't take any
     // further action - an observer will fire when the user does that.
     if (Weave.Status.login == LOGIN_FAILED_LOGIN_REJECTED) {
-      return Promise.reject(new Error("User needs to re-authenticate"));
+      return Promise.reject();
     }
 
     // So - we've a previous auth problem and aren't currently attempting to
@@ -179,6 +160,7 @@ this.BrowserIDManager.prototype = {
     }
     this.resetCredentials();
     this._signedInUser = null;
+    return Promise.resolve();
   },
 
   offerSyncOptions: function () {
@@ -202,7 +184,7 @@ this.BrowserIDManager.prototype = {
 
     // Reset the world before we do anything async.
     this.whenReadyToAuthenticate = Promise.defer();
-    this.whenReadyToAuthenticate.promise.catch(err => {
+    this.whenReadyToAuthenticate.promise.then(null, (err) => {
       this._log.error("Could not authenticate", err);
     });
 
@@ -258,14 +240,14 @@ this.BrowserIDManager.prototype = {
           Services.obs.notifyObservers(null, "weave:service:setup-complete", null);
           Weave.Utils.nextTick(Weave.Service.sync, Weave.Service);
         }
-      }).catch(authErr => {
-        // report what failed...
-        this._log.error("Background fetch for key bundle failed", authErr);
+      }).then(null, err => {
         this._shouldHaveSyncKeyBundle = true; // but we probably don't have one...
-        this.whenReadyToAuthenticate.reject(authErr);
+        this.whenReadyToAuthenticate.reject(err);
+        // report what failed...
+        this._log.error("Background fetch for key bundle failed", err);
       });
       // and we are done - the fetch continues on in the background...
-    }).catch(err => {
+    }).then(null, err => {
       this._log.error("Processing logged in account", err);
     });
   },
@@ -301,8 +283,7 @@ this.BrowserIDManager.prototype = {
       // reauth with the server - in that case we will also get here, but
       // should have the same identity.
       // initializeWithCurrentIdentity will throw and log if these constraints
-      // aren't met (indirectly, via _updateSignedInUser()), so just go ahead
-      // and do the init.
+      // aren't met, so just go ahead and do the init.
       this.initializeWithCurrentIdentity(true);
       break;
 
@@ -311,13 +292,6 @@ this.BrowserIDManager.prototype = {
       // startOver will cause this instance to be thrown away, so there's
       // nothing else to do.
       break;
-
-    case fxAccountsCommon.ON_ACCOUNT_STATE_CHANGE_NOTIFICATION:
-      // throw away token and fetch a new one
-      this.resetCredentials();
-      this._ensureValidToken().catch(err =>
-        this._log.error("Error while fetching a new token", err));
-      break;
     }
   },
 
@@ -413,9 +387,6 @@ this.BrowserIDManager.prototype = {
   resetCredentials: function() {
     this.resetSyncKey();
     this._token = null;
-    // The cluster URL comes from the token, so resetting it to empty will
-    // force Sync to not accidentally use a value from an earlier token.
-    Weave.Service.clusterURL = null;
   },
 
   /**
@@ -503,12 +474,7 @@ this.BrowserIDManager.prototype = {
         // If we still can't get keys it probably means the user authenticated
         // without unlocking the MP or cleared the saved logins, so we've now
         // lost them - the user will need to reauth before continuing.
-        let result;
-        if (this._canFetchKeys()) {
-          result = STATUS_OK;
-        } else {
-          result = LOGIN_FAILED_LOGIN_REJECTED;
-        }
+        let result = this._canFetchKeys() ? STATUS_OK : LOGIN_FAILED_LOGIN_REJECTED;
         log.debug("unlockAndVerifyAuthState re-fetched credentials and is returning", result);
         return result;
       }
@@ -540,27 +506,14 @@ this.BrowserIDManager.prototype = {
     return true;
   },
 
-  // Get our tokenServerURL - a private helper. Returns a string.
-  get _tokenServerUrl() {
-    // We used to support services.sync.tokenServerURI but this was a
-    // pain-point for people using non-default servers as Sync may auto-reset
-    // all services.sync prefs. So if that still exists, it wins.
-    let url = Svc.Prefs.get("tokenServerURI"); // Svc.Prefs "root" is services.sync
-    if (!url) {
-      url = Services.prefs.getCharPref("identity.sync.tokenserver.uri");
-    }
-    while (url.endsWith("/")) { // trailing slashes cause problems...
-      url = url.slice(0, -1);
-    }
-    return url;
-  },
-
   // Refresh the sync token for our user. Returns a promise that resolves
   // with a token (which may be null in one sad edge-case), or rejects with an
   // error.
   _fetchTokenForUser: function() {
-    // tokenServerURI is mis-named - convention is uri means nsISomething...
-    let tokenServerURI = this._tokenServerUrl;
+    let tokenServerURI = Svc.Prefs.get("tokenServerURI");
+    if (tokenServerURI.endsWith("/")) { // trailing slashes cause problems...
+      tokenServerURI = tokenServerURI.slice(0, -1);
+    }
     let log = this._log;
     let client = this._tokenServerClient;
     let fxa = this._fxaService;
@@ -589,7 +542,7 @@ this.BrowserIDManager.prototype = {
       );
     }
 
-    let getToken = assertion => {
+    let getToken = (tokenServerURI, assertion) => {
       log.debug("Getting a token");
       let deferred = Promise.defer();
       let cb = function (err, token) {
@@ -617,18 +570,7 @@ this.BrowserIDManager.prototype = {
     return fxa.whenVerified(this._signedInUser)
       .then(() => maybeFetchKeys())
       .then(() => getAssertion())
-      .then(assertion => getToken(assertion))
-      .catch(err => {
-        // If we get a 401 fetching the token it may be that our certificate
-        // needs to be regenerated.
-        if (!err.response || err.response.status !== 401) {
-          return Promise.reject(err);
-        }
-        log.warn("Token server returned 401, refreshing certificate and retrying token fetch");
-        return fxa.invalidateCertificate()
-          .then(() => getAssertion())
-          .then(assertion => getToken(assertion))
-      })
+      .then(assertion => getToken(tokenServerURI, assertion))
       .then(token => {
         // TODO: Make it be only 80% of the duration, so refresh the token
         // before it actually expires. This is to avoid sync storage errors
@@ -640,18 +582,15 @@ this.BrowserIDManager.prototype = {
         }
         return token;
       })
-      .catch(err => {
+      .then(null, err => {
         // TODO: unify these errors - we need to handle errors thrown by
         // both tokenserverclient and hawkclient.
         // A tokenserver error thrown based on a bad response.
         if (err.response && err.response.status === 401) {
-          err = new AuthenticationError(err, "tokenserver");
+          err = new AuthenticationError(err);
         // A hawkclient error.
         } else if (err.code && err.code === 401) {
-          err = new AuthenticationError(err, "hawkclient");
-        // An FxAccounts.jsm error.
-        } else if (err.message == fxAccountsCommon.ERROR_AUTH_ERROR) {
-          err = new AuthenticationError(err, "fxaccounts");
+          err = new AuthenticationError(err);
         }
 
         // TODO: write tests to make sure that different auth error cases are handled here
@@ -673,6 +612,7 @@ this.BrowserIDManager.prototype = {
         // that there is no authentication dance still under way.
         this._shouldHaveSyncKeyBundle = true;
         Weave.Status.login = this._authFailureReason;
+        Services.obs.notifyObservers(null, "weave:ui:login:error", null);
         throw err;
       });
   },
@@ -684,19 +624,12 @@ this.BrowserIDManager.prototype = {
       this._log.debug("_ensureValidToken already has one");
       return Promise.resolve();
     }
-    const notifyStateChanged =
-      () => Services.obs.notifyObservers(null, "weave:service:login:change", null);
     // reset this._token as a safety net to reduce the possibility of us
     // repeatedly attempting to use an invalid token if _fetchTokenForUser throws.
     this._token = null;
     return this._fetchTokenForUser().then(
       token => {
         this._token = token;
-        notifyStateChanged();
-      },
-      error => {
-        notifyStateChanged();
-        throw error
       }
     );
   },
@@ -719,16 +652,9 @@ this.BrowserIDManager.prototype = {
   _getAuthenticationHeader: function(httpObject, method) {
     let cb = Async.makeSpinningCallback();
     this._ensureValidToken().then(cb, cb);
-    // Note that in failure states we return null, causing the request to be
-    // made without authorization headers, thereby presumably causing a 401,
-    // which causes Sync to log out. If we throw, this may not happen as
-    // expected.
     try {
       cb.wait();
     } catch (ex) {
-      if (Async.isShutdownException(ex)) {
-        throw ex;
-      }
       this._log.error("Failed to fetch a token for authentication", ex);
       return null;
     }
@@ -764,17 +690,8 @@ this.BrowserIDManager.prototype = {
 
   createClusterManager: function(service) {
     return new BrowserIDClusterManager(service);
-  },
+  }
 
-  // Tell Sync what the login status should be if it saw a 401 fetching
-  // info/collections as part of login verification (typically immediately
-  // after login.)
-  // In our case, it almost certainly means a transient error fetching a token
-  // (and hitting this will cause us to logout, which will correctly handle an
-  // authoritative login issue.)
-  loginStatusFromVerification404() {
-    return LOGIN_FAILED_NETWORK_ERROR;
-  },
 };
 
 /* An implementation of the ClusterManager for this identity
@@ -820,7 +737,7 @@ BrowserIDClusterManager.prototype = {
           // it's likely a 401 was received using the existing token - in which
           // case we just discard the existing token and fetch a new one.
           if (this.service.clusterURL) {
-            log.debug("_findCluster has a pre-existing clusterURL, so discarding the current token");
+            log.debug("_findCluster found existing clusterURL, so discarding the current token");
             this.identity._token = null;
           }
           return this.identity._ensureValidToken();
diff --git a/services/sync/modules/collection_validator.js b/services/sync/modules/collection_validator.js
deleted file mode 100644
index 41141bba3..000000000
--- a/services/sync/modules/collection_validator.js
+++ /dev/null
@@ -1,204 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-"use strict";
-
-const Cu = Components.utils;
-
-Cu.import("resource://services-sync/record.js");
-Cu.import("resource://services-sync/main.js");
-
-this.EXPORTED_SYMBOLS = ["CollectionValidator", "CollectionProblemData"];
-
-class CollectionProblemData {
-  constructor() {
-    this.missingIDs = 0;
-    this.duplicates = [];
-    this.clientMissing = [];
-    this.serverMissing = [];
-    this.serverDeleted = [];
-    this.serverUnexpected = [];
-    this.differences = [];
-  }
-
-  /**
-   * Produce a list summarizing problems found. Each entry contains {name, count},
-   * where name is the field name for the problem, and count is the number of times
-   * the problem was encountered.
-   *
-   * Validation has failed if all counts are not 0.
-   */
-  getSummary() {
-    return [
-      { name: "clientMissing", count: this.clientMissing.length },
-      { name: "serverMissing", count: this.serverMissing.length },
-      { name: "serverDeleted", count: this.serverDeleted.length },
-      { name: "serverUnexpected", count: this.serverUnexpected.length },
-      { name: "differences", count: this.differences.length },
-      { name: "missingIDs", count: this.missingIDs },
-      { name: "duplicates", count: this.duplicates.length }
-    ];
-  }
-}
-
-class CollectionValidator {
-  // Construct a generic collection validator. This is intended to be called by
-  // subclasses.
-  // - name: Name of the engine
-  // - idProp: Property that identifies a record. That is, if a client and server
-  //   record have the same value for the idProp property, they should be
-  //   compared against eachother.
-  // - props: Array of properties that should be compared
-  constructor(name, idProp, props) {
-    this.name = name;
-    this.props = props;
-    this.idProp = idProp;
-  }
-
-  // Should a custom ProblemData type be needed, return it here.
-  emptyProblemData() {
-    return new CollectionProblemData();
-  }
-
-  getServerItems(engine) {
-    let collection = engine.itemSource();
-    let collectionKey = engine.service.collectionKeys.keyForCollection(engine.name);
-    collection.full = true;
-    let items = [];
-    collection.recordHandler = function(item) {
-      item.decrypt(collectionKey);
-      items.push(item.cleartext);
-    };
-    let resp = collection.getBatched();
-    if (!resp.success) {
-      throw resp;
-    }
-    return items;
-  }
-
-  // Should return a promise that resolves to an array of client items.
-  getClientItems() {
-    return Promise.reject("Must implement");
-  }
-
-  // Turn the client item into something that can be compared with the server item,
-  // and is also safe to mutate.
-  normalizeClientItem(item) {
-    return Cu.cloneInto(item, {});
-  }
-
-  // Turn the server item into something that can be easily compared with the client
-  // items.
-  normalizeServerItem(item) {
-    return item;
-  }
-
-  // Return whether or not a server item should be present on the client. Expected
-  // to be overridden.
-  clientUnderstands(item) {
-    return true;
-  }
-
-  // Return whether or not a client item should be present on the server. Expected
-  // to be overridden
-  syncedByClient(item) {
-    return true;
-  }
-
-  // Compare the server item and the client item, and return a list of property
-  // names that are different. Can be overridden if needed.
-  getDifferences(client, server) {
-    let differences = [];
-    for (let prop of this.props) {
-      let clientProp = client[prop];
-      let serverProp = server[prop];
-      if ((clientProp || "") !== (serverProp || "")) {
-        differences.push(prop);
-      }
-    }
-    return differences;
-  }
-
-  // Returns an object containing
-  //   problemData: an instance of the class returned by emptyProblemData(),
-  //   clientRecords: Normalized client records
-  //   records: Normalized server records,
-  //   deletedRecords: Array of ids that were marked as deleted by the server.
-  compareClientWithServer(clientItems, serverItems) {
-    clientItems = clientItems.map(item => this.normalizeClientItem(item));
-    serverItems = serverItems.map(item => this.normalizeServerItem(item));
-    let problems = this.emptyProblemData();
-    let seenServer = new Map();
-    let serverDeleted = new Set();
-    let allRecords = new Map();
-
-    for (let record of serverItems) {
-      let id = record[this.idProp];
-      if (!id) {
-        ++problems.missingIDs;
-        continue;
-      }
-      if (record.deleted) {
-        serverDeleted.add(record);
-      } else {
-        let possibleDupe = seenServer.get(id);
-        if (possibleDupe) {
-          problems.duplicates.push(id);
-        } else {
-          seenServer.set(id, record);
-          allRecords.set(id, { server: record, client: null, });
-        }
-        record.understood = this.clientUnderstands(record);
-      }
-    }
-
-    let recordPairs = [];
-    let seenClient = new Map();
-    for (let record of clientItems) {
-      let id = record[this.idProp];
-      record.shouldSync = this.syncedByClient(record);
-      seenClient.set(id, record);
-      let combined = allRecords.get(id);
-      if (combined) {
-        combined.client = record;
-      } else {
-        allRecords.set(id,  { client: record, server: null });
-      }
-    }
-
-    for (let [id, { server, client }] of allRecords) {
-      if (!client && !server) {
-        throw new Error("Impossible: no client or server record for " + id);
-      } else if (server && !client) {
-        if (server.understood) {
-          problems.clientMissing.push(id);
-        }
-      } else if (client && !server) {
-        if (client.shouldSync) {
-          problems.serverMissing.push(id);
-        }
-      } else {
-        if (!client.shouldSync) {
-          if (!problems.serverUnexpected.includes(id)) {
-            problems.serverUnexpected.push(id);
-          }
-          continue;
-        }
-        let differences = this.getDifferences(client, server);
-        if (differences && differences.length) {
-          problems.differences.push({ id, differences });
-        }
-      }
-    }
-    return {
-      problemData: problems,
-      clientRecords: clientItems,
-      records: serverItems,
-      deletedRecords: [...serverDeleted]
-    };
-  }
-}
-
-// Default to 0, some engines may override.
-CollectionValidator.prototype.version = 0;
diff --git a/services/sync/modules/constants.js b/services/sync/modules/constants.js
index f70bbd61c..c8d66d921 100644
--- a/services/sync/modules/constants.js
+++ b/services/sync/modules/constants.js
@@ -4,8 +4,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // Process each item in the "constants hash" to add to "global" and give a name
-this.EXPORTED_SYMBOLS = [];
-for (let [key, val] of Object.entries({
+this.EXPORTED_SYMBOLS = [((this[key] = val), key) for ([key, val] in Iterator({
 
 WEAVE_VERSION:                         "@weave_version@",
 
@@ -45,7 +44,7 @@ MAX_IGNORE_ERROR_COUNT:                5,
 
 // Backoff intervals
 MINIMUM_BACKOFF_INTERVAL:              15 * 60 * 1000,      // 15 minutes
-MAXIMUM_BACKOFF_INTERVAL:              8 * 60 * 60 * 1000,  // 8 hours
+MAXIMUM_BACKOFF_INTERVAL:              8 * 60 * 60 * 1000,  // 8 hours 
 
 // HMAC event handling timeout.
 // 10 minutes: a compromise between the multi-desktop sync interval
@@ -76,10 +75,6 @@ PASSWORDS_STORE_BATCH_SIZE:            50,      // same as MOBILE_BATCH_SIZE
 ADDONS_STORE_BATCH_SIZE:               1000000, // process all addons at once
 APPS_STORE_BATCH_SIZE:                 50,      // same as MOBILE_BATCH_SIZE
 
-// Default batch size for download batching
-// (how many records are fetched at a time from the server when batching is used).
-DEFAULT_DOWNLOAD_BATCH_SIZE:           1000,
-
 // score thresholds for early syncs
 SINGLE_USER_THRESHOLD:                 1000,
 MULTI_DEVICE_THRESHOLD:                300,
@@ -98,16 +93,13 @@ SCORE_UPDATE_DELAY:                    100,
 // observed spurious idle/back events and short enough to pre-empt user activity.
 IDLE_OBSERVER_BACK_DELAY:              100,
 
-// Max number of records or bytes to upload in a single POST - we'll do multiple POSTS if either
-// MAX_UPLOAD_RECORDS or MAX_UPLOAD_BYTES is hit)
+// Number of records to upload in a single POST (multiple POSTS if exceeded)
+// FIXME: Record size limit is 256k (new cluster), so this can be quite large!
+// (Bug 569295)
 MAX_UPLOAD_RECORDS:                    100,
-MAX_UPLOAD_BYTES:                      1024 * 1023, // just under 1MB
 MAX_HISTORY_UPLOAD:                    5000,
 MAX_HISTORY_DOWNLOAD:                  5000,
 
-// TTL of the message sent to another device when sending a tab
-NOTIFY_TAB_SENT_TTL_SECS:              1 * 3600, // 1 hour
-
 // Top-level statuses:
 STATUS_OK:                             "success.status_ok",
 SYNC_FAILED:                           "error.sync.failed",
@@ -130,6 +122,7 @@ LOGIN_FAILED_NETWORK_ERROR:            "error.login.reason.network",
 LOGIN_FAILED_SERVER_ERROR:             "error.login.reason.server",
 LOGIN_FAILED_INVALID_PASSPHRASE:       "error.login.reason.recoverykey",
 LOGIN_FAILED_LOGIN_REJECTED:           "error.login.reason.account",
+LOGIN_FAILED_NOT_READY:                "error.login.reason.initializing",
 
 // sync failure status codes
 METARECORD_DOWNLOAD_FAIL:              "error.sync.reason.metarecord_download_fail",
@@ -152,8 +145,6 @@ ENGINE_UNKNOWN_FAIL:                   "error.engine.reason.unknown_fail",
 ENGINE_APPLY_FAIL:                     "error.engine.reason.apply_fail",
 ENGINE_METARECORD_DOWNLOAD_FAIL:       "error.engine.reason.metarecord_download_fail",
 ENGINE_METARECORD_UPLOAD_FAIL:         "error.engine.reason.metarecord_upload_fail",
-// an upload failure where the batch was interrupted with a 412
-ENGINE_BATCH_INTERRUPTED:              "error.engine.reason.batch_interrupted",
 
 JPAKE_ERROR_CHANNEL:                   "jpake.error.channel",
 JPAKE_ERROR_NETWORK:                   "jpake.error.network",
@@ -181,7 +172,7 @@ kSyncBackoffNotMet:                    "Trying to sync before the server said it
 kFirstSyncChoiceNotMade:               "User has not selected an action for first sync",
 
 // Application IDs
-FIREFOX_ID:                            "{ec8030f7-c20a-464f-9b0e-13a3a9e97384}",
+FIREFOX_ID:                            "{8de7fcbb-c55c-4fbe-bfc5-fc555c87dbc4}",
 FENNEC_ID:                             "{a23983c0-fd0e-11dc-95ff-0800200c9a66}",
 SEAMONKEY_ID:                          "{92650c4d-4b8e-4d2a-b7eb-24ecf4f6b63a}",
 TEST_HARNESS_ID:                       "xuth@mozilla.org",
@@ -189,10 +180,6 @@ TEST_HARNESS_ID:                       "xuth@mozilla.org",
 MIN_PP_LENGTH:                         12,
 MIN_PASS_LENGTH:                       8,
 
-DEVICE_TYPE_DESKTOP:                   "desktop",
-DEVICE_TYPE_MOBILE:                    "mobile",
+LOG_DATE_FORMAT:                       "%Y-%m-%d %H:%M:%S",
 
-})) {
-  this[key] = val;
-  this.EXPORTED_SYMBOLS.push(key);
-}
+}))];
diff --git a/services/sync/modules/engines.js b/services/sync/modules/engines.js
index 1eaa1863a..eabddae2b 100644
--- a/services/sync/modules/engines.js
+++ b/services/sync/modules/engines.js
@@ -7,24 +7,21 @@ this.EXPORTED_SYMBOLS = [
   "Engine",
   "SyncEngine",
   "Tracker",
-  "Store",
-  "Changeset"
+  "Store"
 ];
 
-var {classes: Cc, interfaces: Ci, results: Cr, utils: Cu} = Components;
+const {classes: Cc, interfaces: Ci, results: Cr, utils: Cu} = Components;
 
 Cu.import("resource://services-common/async.js");
 Cu.import("resource://gre/modules/Log.jsm");
 Cu.import("resource://services-common/observers.js");
+Cu.import("resource://services-common/utils.js");
 Cu.import("resource://services-sync/constants.js");
 Cu.import("resource://services-sync/identity.js");
 Cu.import("resource://services-sync/record.js");
 Cu.import("resource://services-sync/resource.js");
 Cu.import("resource://services-sync/util.js");
 
-XPCOMUtils.defineLazyModuleGetter(this, "fxAccounts",
-  "resource://gre/modules/FxAccounts.jsm");
-
 /*
  * Trackers are associated with a single engine and deal with
  * listening for changes to their particular data type.
@@ -107,7 +104,7 @@ Tracker.prototype = {
     Utils.jsonLoad("changes/" + this.file, this, function(json) {
       if (json && (typeof(json) == "object")) {
         this.changedIDs = json;
-      } else if (json !== null) {
+      } else {
         this._log.warn("Changed IDs file " + this.file + " contains non-object value.");
         json = null;
       }
@@ -132,30 +129,26 @@ Tracker.prototype = {
       this._ignored.splice(index, 1);
   },
 
-  _saveChangedID(id, when) {
-    this._log.trace(`Adding changed ID: ${id}, ${JSON.stringify(when)}`);
-    this.changedIDs[id] = when;
-    this.saveChangedIDs(this.onSavedChangedIDs);
-  },
-
   addChangedID: function (id, when) {
     if (!id) {
       this._log.warn("Attempted to add undefined ID to tracker");
       return false;
     }
 
-    if (this.ignoreAll || this._ignored.includes(id)) {
+    if (this.ignoreAll || (id in this._ignored)) {
       return false;
     }
 
     // Default to the current time in seconds if no time is provided.
     if (when == null) {
-      when = this._now();
+      when = Math.floor(Date.now() / 1000);
     }
 
     // Add/update the entry if we have a newer time.
     if ((this.changedIDs[id] || -Infinity) < when) {
-      this._saveChangedID(id, when);
+      this._log.trace("Adding changed ID: " + id + ", " + when);
+      this.changedIDs[id] = when;
+      this.saveChangedIDs(this.onSavedChangedIDs);
     }
 
     return true;
@@ -166,9 +159,8 @@ Tracker.prototype = {
       this._log.warn("Attempted to remove undefined ID to tracker");
       return false;
     }
-    if (this.ignoreAll || this._ignored.includes(id)) {
+    if (this.ignoreAll || (id in this._ignored))
       return false;
-    }
     if (this.changedIDs[id] != null) {
       this._log.trace("Removing changed ID " + id);
       delete this.changedIDs[id];
@@ -183,10 +175,6 @@ Tracker.prototype = {
     this.saveChangedIDs();
   },
 
-  _now() {
-    return Date.now() / 1000;
-  },
-
   _isTracking: false,
 
   // Override these in your subclasses.
@@ -311,21 +299,17 @@ Store.prototype = {
    */
   applyIncomingBatch: function (records) {
     let failed = [];
-    for (let record of records) {
+    for each (let record in records) {
       try {
         this.applyIncoming(record);
+      } catch (ex if (ex.code == Engine.prototype.eEngineAbortApplyIncoming)) {
+        // This kind of exception should have a 'cause' attribute, which is an
+        // originating exception.
+        // ex.cause will carry its stack with it when rethrown.
+        throw ex.cause;
       } catch (ex) {
-        if (ex.code == Engine.prototype.eEngineAbortApplyIncoming) {
-          // This kind of exception should have a 'cause' attribute, which is an
-          // originating exception.
-          // ex.cause will carry its stack with it when rethrown.
-          throw ex.cause;
-        }
-        if (Async.isShutdownException(ex)) {
-          throw ex;
-        }
-        this._log.warn("Failed to apply incoming record " + record.id, ex);
-        this.engine._noteApplyFailure();
+        this._log.warn("Failed to apply incoming record " + record.id);
+        this._log.warn("Encountered exception: " + Utils.exceptionStr(ex));
         failed.push(record.id);
       }
     };
@@ -499,11 +483,7 @@ EngineManager.prototype = {
   },
 
   getAll: function () {
-    let engines = [];
-    for (let [, engine] of Object.entries(this._engines)) {
-      engines.push(engine);
-    }
-    return engines;
+    return [engine for ([name, engine] in Iterator(this._engines))];
   },
 
   /**
@@ -516,7 +496,7 @@ EngineManager.prototype = {
   },
 
   get enabledEngineNames() {
-    return this.getEnabled().map(e => e.name);
+    return [e.name for each (e in this.getEnabled())];
   },
 
   persistDeclined: function () {
@@ -593,11 +573,16 @@ EngineManager.prototype = {
         this._engines[name] = engine;
       }
     } catch (ex) {
+      this._log.error(CommonUtils.exceptionStr(ex));
+
+      let mesg = ex.message ? ex.message : ex;
       let name = engineObject || "";
       name = name.prototype || "";
       name = name.name || "";
 
-      this._log.error(`Could not initialize engine ${name}`, ex);
+      let out = "Could not initialize engine '" + name + "': " + mesg;
+      this._log.error(out);
+
       return engineObject;
     }
   },
@@ -643,17 +628,16 @@ Engine.prototype = {
   // Signal to the engine that processing further records is pointless.
   eEngineAbortApplyIncoming: "error.engine.abort.applyincoming",
 
-  // Should we keep syncing if we find a record that cannot be uploaded (ever)?
-  // If this is false, we'll throw, otherwise, we'll ignore the record and
-  // continue. This currently can only happen due to the record being larger
-  // than the record upload limit.
-  allowSkippedRecord: true,
-
   get prefName() {
     return this.name;
   },
 
   get enabled() {
+    // XXX: Disable non-functional add-ons syncing for the time being
+    // This check can go away when add-on syncing is addressed
+    if (this.prefName == "addons")
+      return false;
+
     return Svc.Prefs.get("engine." + this.prefName, false);
   },
 
@@ -711,15 +695,6 @@ Engine.prototype = {
 
   wipeClient: function () {
     this._notify("wipe-client", this.name, this._wipeClient)();
-  },
-
-  /**
-   * If one exists, initialize and return a validator for this engine (which
-   * must have a `validate(engine)` method that returns a promise to an object
-   * with a getSummary method). Otherwise return null.
-   */
-  getValidator: function () {
-    return null;
   }
 };
 
@@ -813,11 +788,7 @@ SyncEngine.prototype = {
     return this._toFetch;
   },
   set toFetch(val) {
-    let cb = (error) => {
-      if (error) {
-        this._log.error("Failed to read JSON records to fetch", error);
-      }
-    }
+    let cb = (error) => this._log.error(Utils.exceptionStr(error));
     // Coerce the array to a string for more efficient comparison.
     if (val + "" == this._toFetch) {
       return;
@@ -842,13 +813,7 @@ SyncEngine.prototype = {
     return this._previousFailed;
   },
   set previousFailed(val) {
-    let cb = (error) => {
-      if (error) {
-        this._log.error("Failed to set previousFailed", error);
-      } else {
-        this._log.debug("Successfully wrote previousFailed.");
-      }
-    }
+    let cb = (error) => this._log.error(Utils.exceptionStr(error));
     // Coerce the array to a string for more efficient comparison.
     if (val + "" == this._previousFailed) {
       return;
@@ -881,8 +846,9 @@ SyncEngine.prototype = {
   },
 
   /*
-   * Returns a changeset for this sync. Engine implementations can override this
-   * method to bypass the tracker for certain or all changed items.
+   * Returns a mapping of IDs -> changed timestamp. Engine implementations
+   * can override this method to bypass the tracker for certain or all
+   * changed items.
    */
   getChangedIDs: function () {
     return this._tracker.changedIDs;
@@ -950,16 +916,20 @@ SyncEngine.prototype = {
     // this._modified to the tracker.
     this.lastSyncLocal = Date.now();
     if (this.lastSync) {
-      this._modified = this.pullNewChanges();
+      this._modified = this.getChangedIDs();
     } else {
+      // Mark all items to be uploaded, but treat them as changed from long ago
       this._log.debug("First sync, uploading all items");
-      this._modified = this.pullAllChanges();
+      this._modified = {};
+      for (let id in this._store.getAllIDs()) {
+        this._modified[id] = 0;
+      }
     }
     // Clear the tracker now. If the sync fails we'll add the ones we failed
     // to upload back.
     this._tracker.clearChangedIDs();
 
-    this._log.info(this._modified.count() +
+    this._log.info(Object.keys(this._modified).length +
                    " outgoing items pre-reconciliation");
 
     // Keep track of what to delete at the end of sync
@@ -970,7 +940,7 @@ SyncEngine.prototype = {
    * A tiny abstraction to make it easier to test incoming record
    * application.
    */
-  itemSource: function () {
+  _itemSource: function () {
     return new Collection(this.engineURL, this._recordObj, this.service);
   },
 
@@ -987,7 +957,7 @@ SyncEngine.prototype = {
     let isMobile = (Svc.Prefs.get("client.type") == "mobile");
 
     if (!newitems) {
-      newitems = this.itemSource();
+      newitems = this._itemSource();
     }
 
     if (this._defaultSort) {
@@ -1024,12 +994,10 @@ SyncEngine.prototype = {
       try {
         failed = failed.concat(this._store.applyIncomingBatch(applyBatch));
       } catch (ex) {
-        if (Async.isShutdownException(ex)) {
-          throw ex;
-        }
         // Catch any error that escapes from applyIncomingBatch. At present
         // those will all be abort events.
-        this._log.warn("Got exception, aborting processIncoming", ex);
+        this._log.warn("Got exception " + Utils.exceptionStr(ex) +
+                       ", aborting processIncoming.");
         aborting = ex;
       }
       this._tracker.ignoreAll = false;
@@ -1074,10 +1042,7 @@ SyncEngine.prototype = {
       try {
         try {
           item.decrypt(key);
-        } catch (ex) {
-          if (!Utils.isHMACMismatch(ex)) {
-            throw ex;
-          }
+        } catch (ex if Utils.isHMACMismatch(ex)) {
           let strategy = self.handleHMACMismatch(item, true);
           if (strategy == SyncEngine.kRecoveryStrategy.retry) {
             // You only get one retry.
@@ -1087,10 +1052,7 @@ SyncEngine.prototype = {
               key = self.service.collectionKeys.keyForCollection(self.name);
               item.decrypt(key);
               strategy = null;
-            } catch (ex) {
-              if (!Utils.isHMACMismatch(ex)) {
-                throw ex;
-              }
+            } catch (ex if Utils.isHMACMismatch(ex)) {
               strategy = self.handleHMACMismatch(item, false);
             }
           }
@@ -1103,8 +1065,7 @@ SyncEngine.prototype = {
               self._log.debug("Ignoring second retry suggestion.");
               // Fall through to error case.
             case SyncEngine.kRecoveryStrategy.error:
-              self._log.warn("Error decrypting record", ex);
-              self._noteApplyFailure();
+              self._log.warn("Error decrypting record: " + Utils.exceptionStr(ex));
               failed.push(item.id);
               return;
             case SyncEngine.kRecoveryStrategy.ignore:
@@ -1114,11 +1075,7 @@ SyncEngine.prototype = {
           }
         }
       } catch (ex) {
-        if (Async.isShutdownException(ex)) {
-          throw ex;
-        }
-        self._log.warn("Error decrypting record", ex);
-        self._noteApplyFailure();
+        self._log.warn("Error decrypting record: " + Utils.exceptionStr(ex));
         failed.push(item.id);
         return;
       }
@@ -1126,20 +1083,15 @@ SyncEngine.prototype = {
       let shouldApply;
       try {
         shouldApply = self._reconcile(item);
+      } catch (ex if (ex.code == Engine.prototype.eEngineAbortApplyIncoming)) {
+        self._log.warn("Reconciliation failed: aborting incoming processing.");
+        failed.push(item.id);
+        aborting = ex.cause;
       } catch (ex) {
-        if (ex.code == Engine.prototype.eEngineAbortApplyIncoming) {
-          self._log.warn("Reconciliation failed: aborting incoming processing.");
-          self._noteApplyFailure();
-          failed.push(item.id);
-          aborting = ex.cause;
-        } else if (!Async.isShutdownException(ex)) {
-          self._log.warn("Failed to reconcile incoming record " + item.id, ex);
-          self._noteApplyFailure();
-          failed.push(item.id);
-          return;
-        } else {
-          throw ex;
-        }
+        self._log.warn("Failed to reconcile incoming record " + item.id);
+        self._log.warn("Encountered exception: " + Utils.exceptionStr(ex));
+        failed.push(item.id);
+        return;
       }
 
       if (shouldApply) {
@@ -1158,7 +1110,7 @@ SyncEngine.prototype = {
 
     // Only bother getting data from the server if there's new things
     if (this.lastModified == null || this.lastModified > this.lastSync) {
-      let resp = newitems.getBatched();
+      let resp = newitems.get();
       doApplyBatchAndPersistFailed.call(this);
       if (!resp.success) {
         resp.failureCode = ENGINE_DOWNLOAD_FAIL;
@@ -1243,13 +1195,7 @@ SyncEngine.prototype = {
     // Apply remaining items.
     doApplyBatchAndPersistFailed.call(this);
 
-    count.newFailed = this.previousFailed.reduce((count, engine) => {
-      if (failedInPreviousSync.indexOf(engine) == -1) {
-        count++;
-        this._noteApplyNewFailure();
-      }
-      return count;
-    }, 0);
+    count.newFailed = Utils.arraySub(this.previousFailed, failedInPreviousSync).length;
     count.succeeded = Math.max(0, count.applied - count.failed);
     this._log.info(["Records:",
                     count.applied, "applied,",
@@ -1260,14 +1206,6 @@ SyncEngine.prototype = {
     Observers.notify("weave:engine:sync:applied", count, this.name);
   },
 
-  _noteApplyFailure: function () {
-    // here would be a good place to record telemetry...
-  },
-
-  _noteApplyNewFailure: function () {
-    // here would be a good place to record telemetry...
-  },
-
   /**
    * Find a GUID of an item that is a duplicate of the incoming item but happens
    * to have a different GUID
@@ -1278,16 +1216,6 @@ SyncEngine.prototype = {
     // By default, assume there's no dupe items for the engine
   },
 
-  // Called when the server has a record marked as deleted, but locally we've
-  // changed it more recently than the deletion. If we return false, the
-  // record will be deleted locally. If we return true, we'll reupload the
-  // record to the server -- any extra work that's needed as part of this
-  // process should be done at this point (such as mark the record's parent
-  // for reuploading in the case of bookmarks).
-  _shouldReviveRemotelyDeletedRecord(remoteItem) {
-    return true;
-  },
-
   _deleteId: function (id) {
     this._tracker.removeChangedID(id);
 
@@ -1298,18 +1226,6 @@ SyncEngine.prototype = {
       this._delete.ids.push(id);
   },
 
-  _switchItemToDupe(localDupeGUID, incomingItem) {
-    // The local, duplicate ID is always deleted on the server.
-    this._deleteId(localDupeGUID);
-
-    // We unconditionally change the item's ID in case the engine knows of
-    // an item but doesn't expose it through itemExists. If the API
-    // contract were stronger, this could be changed.
-    this._log.debug("Switching local ID to incoming: " + localDupeGUID + " -> " +
-                    incomingItem.id);
-    this._store.changeItemID(localDupeGUID, incomingItem.id);
-  },
-
   /**
    * Reconcile incoming record with local state.
    *
@@ -1329,12 +1245,12 @@ SyncEngine.prototype = {
     // because some state may change during the course of this function and we
     // need to operate on the original values.
     let existsLocally   = this._store.itemExists(item.id);
-    let locallyModified = this._modified.has(item.id);
+    let locallyModified = item.id in this._modified;
 
     // TODO Handle clock drift better. Tracked in bug 721181.
     let remoteAge = AsyncResource.serverTime - item.modified;
     let localAge  = locallyModified ?
-      (Date.now() / 1000 - this._modified.getModifiedTimestamp(item.id)) : null;
+      (Date.now() / 1000 - this._modified[item.id]) : null;
     let remoteIsNewer = remoteAge < localAge;
 
     this._log.trace("Reconciling " + item.id + ". exists=" +
@@ -1363,18 +1279,15 @@ SyncEngine.prototype = {
                         "exists and isn't modified.");
         return true;
       }
-      this._log.trace("Incoming record is deleted but we had local changes.");
 
-      if (remoteIsNewer) {
-        this._log.trace("Remote record is newer -- deleting local record.");
-        return true;
-      }
-      // If the local record is newer, we defer to individual engines for
-      // how to handle this. By default, we revive the record.
-      let willRevive = this._shouldReviveRemotelyDeletedRecord(item);
-      this._log.trace("Local record is newer -- reviving? " + willRevive);
-
-      return !willRevive;
+      // TODO As part of bug 720592, determine whether we should do more here.
+      // In the case where the local changes are newer, it is quite possible
+      // that the local client will restore data a remote client had tried to
+      // delete. There might be a good reason for that delete and it might be
+      // enexpected for this client to restore that data.
+      this._log.trace("Incoming record is deleted but we had local changes. " +
+                      "Applying the youngest record.");
+      return remoteIsNewer;
     }
 
     // At this point the incoming record is not for a deletion and must have
@@ -1386,32 +1299,40 @@ SyncEngine.prototype = {
     // refresh the metadata collected above. See bug 710448 for the history
     // of this logic.
     if (!existsLocally) {
-      let localDupeGUID = this._findDupe(item);
-      if (localDupeGUID) {
-        this._log.trace("Local item " + localDupeGUID + " is a duplicate for " +
+      let dupeID = this._findDupe(item);
+      if (dupeID) {
+        this._log.trace("Local item " + dupeID + " is a duplicate for " +
                         "incoming item " + item.id);
 
+        // The local, duplicate ID is always deleted on the server.
+        this._deleteId(dupeID);
+
         // The current API contract does not mandate that the ID returned by
         // _findDupe() actually exists. Therefore, we have to perform this
         // check.
-        existsLocally = this._store.itemExists(localDupeGUID);
+        existsLocally = this._store.itemExists(dupeID);
+
+        // We unconditionally change the item's ID in case the engine knows of
+        // an item but doesn't expose it through itemExists. If the API
+        // contract were stronger, this could be changed.
+        this._log.debug("Switching local ID to incoming: " + dupeID + " -> " +
+                        item.id);
+        this._store.changeItemID(dupeID, item.id);
 
         // If the local item was modified, we carry its metadata forward so
         // appropriate reconciling can be performed.
-        if (this._modified.has(localDupeGUID)) {
+        if (dupeID in this._modified) {
           locallyModified = true;
-          localAge = this._tracker._now() - this._modified.getModifiedTimestamp(localDupeGUID);
+          localAge = Date.now() / 1000 - this._modified[dupeID];
           remoteIsNewer = remoteAge < localAge;
 
-          this._modified.swap(localDupeGUID, item.id);
+          this._modified[item.id] = this._modified[dupeID];
+          delete this._modified[dupeID];
         } else {
           locallyModified = false;
           localAge = null;
         }
 
-        // Tell the engine to do whatever it needs to switch the items.
-        this._switchItemToDupe(localDupeGUID, item);
-
         this._log.debug("Local item after duplication: age=" + localAge +
                         "; modified=" + locallyModified + "; exists=" +
                         existsLocally);
@@ -1440,7 +1361,7 @@ SyncEngine.prototype = {
       if (remoteIsNewer) {
         this._log.trace("Applying incoming because local item was deleted " +
                         "before the incoming item was changed.");
-        this._modified.delete(item.id);
+        delete this._modified[item.id];
         return true;
       }
 
@@ -1466,7 +1387,7 @@ SyncEngine.prototype = {
       this._log.trace("Ignoring incoming item because the local item is " +
                       "identical.");
 
-      this._modified.delete(item.id);
+      delete this._modified[item.id];
       return false;
     }
 
@@ -1491,97 +1412,69 @@ SyncEngine.prototype = {
   _uploadOutgoing: function () {
     this._log.trace("Uploading local changes to server.");
 
-    let modifiedIDs = this._modified.ids();
+    let modifiedIDs = Object.keys(this._modified);
     if (modifiedIDs.length) {
       this._log.trace("Preparing " + modifiedIDs.length +
                       " outgoing records");
 
-      let counts = { sent: modifiedIDs.length, failed: 0 };
-
       // collection we'll upload
       let up = new Collection(this.engineURL, null, this.service);
+      let count = 0;
 
-      let failed = [];
-      let successful = [];
-      let handleResponse = (resp, batchOngoing = false) => {
-        // Note: We don't want to update this.lastSync, or this._modified until
-        // the batch is complete, however we want to remember success/failure
-        // indicators for when that happens.
+      // Upload what we've got so far in the collection
+      let doUpload = Utils.bind2(this, function(desc) {
+        this._log.info("Uploading " + desc + " of " + modifiedIDs.length +
+                       " records");
+        let resp = up.post();
         if (!resp.success) {
           this._log.debug("Uploading records failed: " + resp);
-          resp.failureCode = resp.status == 412 ? ENGINE_BATCH_INTERRUPTED : ENGINE_UPLOAD_FAIL;
+          resp.failureCode = ENGINE_UPLOAD_FAIL;
           throw resp;
         }
 
         // Update server timestamp from the upload.
-        failed = failed.concat(Object.keys(resp.obj.failed));
-        successful = successful.concat(resp.obj.success);
-
-        if (batchOngoing) {
-          // Nothing to do yet
-          return;
-        }
-        // Advance lastSync since we've finished the batch.
         let modified = resp.headers["x-weave-timestamp"];
-        if (modified > this.lastSync) {
+        if (modified > this.lastSync)
           this.lastSync = modified;
-        }
-        if (failed.length && this._log.level <= Log.Level.Debug) {
+
+        let failed_ids = Object.keys(resp.obj.failed);
+        if (failed_ids.length)
           this._log.debug("Records that will be uploaded again because "
                           + "the server couldn't store them: "
-                          + failed.join(", "));
-        }
-
-        counts.failed += failed.length;
+                          + failed_ids.join(", "));
 
-        for (let id of successful) {
-          this._modified.delete(id);
+        // Clear successfully uploaded objects.
+        for each (let id in resp.obj.success) {
+          delete this._modified[id];
         }
 
-        this._onRecordsWritten(successful, failed);
-
-        // clear for next batch
-        failed.length = 0;
-        successful.length = 0;
-      };
-
-      let postQueue = up.newPostQueue(this._log, this.lastSync, handleResponse);
+        up.clearRecords();
+      });
 
-      for (let id of modifiedIDs) {
-        let out;
-        let ok = false;
+      for each (let id in modifiedIDs) {
         try {
-          out = this._createRecord(id);
+          let out = this._createRecord(id);
           if (this._log.level <= Log.Level.Trace)
             this._log.trace("Outgoing: " + out);
 
           out.encrypt(this.service.collectionKeys.keyForCollection(this.name));
-          ok = true;
-        } catch (ex) {
-          if (Async.isShutdownException(ex)) {
-            throw ex;
-          }
-          this._log.warn("Error creating record", ex);
+          up.pushData(out);
         }
-        if (ok) {
-          let { enqueued, error } = postQueue.enqueue(out);
-          if (!enqueued) {
-            ++counts.failed;
-            if (!this.allowSkippedRecord) {
-              throw error;
-            }
-          }
+        catch(ex) {
+          this._log.warn("Error creating record: " + Utils.exceptionStr(ex));
         }
+
+        // Partial upload
+        if ((++count % MAX_UPLOAD_RECORDS) == 0)
+          doUpload((count - MAX_UPLOAD_RECORDS) + " - " + count + " out");
+
         this._store._sleep(0);
       }
-      postQueue.flush(true);
-      Observers.notify("weave:engine:sync:uploaded", counts, this.name);
-    }
-  },
 
-  _onRecordsWritten(succeeded, failed) {
-    // Implement this method to take specific actions against successfully
-    // uploaded records and failed records.
+      // Final upload
+      if (count % MAX_UPLOAD_RECORDS > 0)
+        doUpload(count >= MAX_UPLOAD_RECORDS ? "last batch" : "all");
+    }
   },
 
   // Any cleanup necessary.
@@ -1596,7 +1489,7 @@ SyncEngine.prototype = {
       coll.delete();
     });
 
-    for (let [key, val] of Object.entries(this._delete)) {
+    for (let [key, val] in Iterator(this._delete)) {
       // Remove the key for future uses
       delete this._delete[key];
 
@@ -1619,8 +1512,10 @@ SyncEngine.prototype = {
     }
 
     // Mark failed WBOs as changed again so they are reuploaded next time.
-    this.trackRemainingChanges();
-    this._modified.clear();
+    for (let [id, when] in Iterator(this._modified)) {
+      this._tracker.addChangedID(id, when);
+    }
+    this._modified = {};
   },
 
   _sync: function () {
@@ -1656,11 +1551,9 @@ SyncEngine.prototype = {
     try {
       this._log.trace("Trying to decrypt a record from the server..");
       test.get();
-    } catch (ex) {
-      if (Async.isShutdownException(ex)) {
-        throw ex;
-      }
-      this._log.debug("Failed test decrypt", ex);
+    }
+    catch(ex) {
+      this._log.debug("Failed test decrypt: " + Utils.exceptionStr(ex));
     }
 
     return canDecrypt;
@@ -1706,108 +1599,5 @@ SyncEngine.prototype = {
     return (this.service.handleHMACEvent() && mayRetry) ?
            SyncEngine.kRecoveryStrategy.retry :
            SyncEngine.kRecoveryStrategy.error;
-  },
-
-  /**
-   * Returns a changeset containing all items in the store. The default
-   * implementation returns a changeset with timestamps from long ago, to
-   * ensure we always use the remote version if one exists.
-   *
-   * This function is only called for the first sync. Subsequent syncs call
-   * `pullNewChanges`.
-   *
-   * @return A `Changeset` object.
-   */
-  pullAllChanges() {
-    let changeset = new Changeset();
-    for (let id in this._store.getAllIDs()) {
-      changeset.set(id, 0);
-    }
-    return changeset;
-  },
-
-  /*
-   * Returns a changeset containing entries for all currently tracked items.
-   * The default implementation returns a changeset with timestamps indicating
-   * when the item was added to the tracker.
-   *
-   * @return A `Changeset` object.
-   */
-  pullNewChanges() {
-    return new Changeset(this.getChangedIDs());
-  },
-
-  /**
-   * Adds all remaining changeset entries back to the tracker, typically for
-   * items that failed to upload. This method is called at the end of each sync.
-   *
-   */
-  trackRemainingChanges() {
-    for (let [id, change] of this._modified.entries()) {
-      this._tracker.addChangedID(id, change);
-    }
-  },
-};
-
-/**
- * A changeset is created for each sync in `Engine::get{Changed, All}IDs`,
- * and stores opaque change data for tracked IDs. The default implementation
- * only records timestamps, though engines can extend this to store additional
- * data for each entry.
- */
-class Changeset {
-  // Creates a changeset with an initial set of tracked entries.
-  constructor(changes = {}) {
-    this.changes = changes;
-  }
-
-  // Returns the last modified time, in seconds, for an entry in the changeset.
-  // `id` is guaranteed to be in the set.
-  getModifiedTimestamp(id) {
-    return this.changes[id];
-  }
-
-  // Adds a change for a tracked ID to the changeset.
-  set(id, change) {
-    this.changes[id] = change;
-  }
-
-  // Indicates whether an entry is in the changeset.
-  has(id) {
-    return id in this.changes;
   }
-
-  // Deletes an entry from the changeset. Used to clean up entries for
-  // reconciled and successfully uploaded records.
-  delete(id) {
-    delete this.changes[id];
-  }
-
-  // Swaps two entries in the changeset. Used when reconciling duplicates that
-  // have local changes.
-  swap(oldID, newID) {
-    this.changes[newID] = this.changes[oldID];
-    delete this.changes[oldID];
-  }
-
-  // Returns an array of all tracked IDs in this changeset.
-  ids() {
-    return Object.keys(this.changes);
-  }
-
-  // Returns an array of `[id, change]` tuples. Used to repopulate the tracker
-  // with entries for failed uploads at the end of a sync.
-  entries() {
-    return Object.entries(this.changes);
-  }
-
-  // Returns the number of entries in this changeset.
-  count() {
-    return this.ids().length;
-  }
-
-  // Clears the changeset.
-  clear() {
-    this.changes = {};
-  }
-}
+};
diff --git a/services/sync/modules/engines/addons.js b/services/sync/modules/engines/addons.js
index 01dab58d1..ab3131c30 100644
--- a/services/sync/modules/engines/addons.js
+++ b/services/sync/modules/engines/addons.js
@@ -25,18 +25,15 @@
  *
  * Synchronization is influenced by the following preferences:
  *
+ *  - services.sync.addons.ignoreRepositoryChecking
  *  - services.sync.addons.ignoreUserEnabledChanges
  *  - services.sync.addons.trustedSourceHostnames
  *
- *  and also influenced by whether addons have repository caching enabled and
- *  whether they allow installation of addons from insecure options (both of
- *  which are themselves influenced by the "extensions." pref branch)
- *
  * See the documentation in services-sync.js for the behavior of these prefs.
  */
 "use strict";
 
-var {classes: Cc, interfaces: Ci, utils: Cu} = Components;
+const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
 
 Cu.import("resource://services-sync/addonutils.js");
 Cu.import("resource://services-sync/addonsreconciler.js");
@@ -44,7 +41,6 @@ Cu.import("resource://services-sync/engines.js");
 Cu.import("resource://services-sync/record.js");
 Cu.import("resource://services-sync/util.js");
 Cu.import("resource://services-sync/constants.js");
-Cu.import("resource://services-sync/collection_validator.js");
 Cu.import("resource://services-common/async.js");
 
 Cu.import("resource://gre/modules/Preferences.jsm");
@@ -54,7 +50,7 @@ XPCOMUtils.defineLazyModuleGetter(this, "AddonManager",
 XPCOMUtils.defineLazyModuleGetter(this, "AddonRepository",
                                   "resource://gre/modules/addons/AddonRepository.jsm");
 
-this.EXPORTED_SYMBOLS = ["AddonsEngine", "AddonValidator"];
+this.EXPORTED_SYMBOLS = ["AddonsEngine"];
 
 // 7 days in milliseconds.
 const PRUNE_ADDON_CHANGES_THRESHOLD = 60 * 60 * 24 * 7 * 1000;
@@ -154,7 +150,7 @@ AddonsEngine.prototype = {
    */
   getChangedIDs: function getChangedIDs() {
     let changes = {};
-    for (let [id, modified] of Object.entries(this._tracker.changedIDs)) {
+    for (let [id, modified] in Iterator(this._tracker.changedIDs)) {
       changes[id] = modified;
     }
 
@@ -164,7 +160,7 @@ AddonsEngine.prototype = {
     // we assume this function is only called from within a sync.
     let reconcilerChanges = this._reconciler.getChangesSinceDate(lastSyncDate);
     let addons = this._reconciler.addons;
-    for (let change of reconcilerChanges) {
+    for each (let change in reconcilerChanges) {
       let changeTime = change[0];
       let id = change[2];
 
@@ -177,7 +173,7 @@ AddonsEngine.prototype = {
           continue;
       }
 
-      if (!this.isAddonSyncable(addons[id])) {
+      if (!this._store.isAddonSyncable(addons[id])) {
         continue;
       }
 
@@ -235,10 +231,6 @@ AddonsEngine.prototype = {
     let cb = Async.makeSpinningCallback();
     this._reconciler.refreshGlobalState(cb);
     cb.wait();
-  },
-
-  isAddonSyncable(addon, ignoreRepoCheck) {
-    return this._store.isAddonSyncable(addon, ignoreRepoCheck);
   }
 };
 
@@ -286,14 +278,6 @@ AddonsStore.prototype = {
       }
     }
 
-    // Ignore incoming records for which an existing non-syncable addon
-    // exists.
-    let existingMeta = this.reconciler.addons[record.addonID];
-    if (existingMeta && !this.isAddonSyncable(existingMeta)) {
-      this._log.info("Ignoring incoming record for an existing but non-syncable addon", record.addonID);
-      return;
-    }
-
     Store.prototype.applyIncoming.call(this, record);
   },
 
@@ -307,23 +291,15 @@ AddonsStore.prototype = {
       id:               record.addonID,
       syncGUID:         record.id,
       enabled:          record.enabled,
-      requireSecureURI: this._extensionsPrefs.get("install.requireSecureOrigin", true),
+      requireSecureURI: !Svc.Prefs.get("addons.ignoreRepositoryChecking", false),
     }], cb);
 
     // This will throw if there was an error. This will get caught by the sync
     // engine and the record will try to be applied later.
     let results = cb.wait();
 
-    if (results.skipped.includes(record.addonID)) {
-      this._log.info("Add-on skipped: " + record.addonID);
-      // Just early-return for skipped addons - we don't want to arrange to
-      // try again next time because the condition that caused up to skip
-      // will remain true for this addon forever.
-      return;
-    }
-
     let addon;
-    for (let a of results.addons) {
+    for each (let a in results.addons) {
       if (a.id == record.addonID) {
         addon = a;
         break;
@@ -467,8 +443,7 @@ AddonsStore.prototype = {
     let ids = {};
 
     let addons = this.reconciler.addons;
-    for (let id in addons) {
-      let addon = addons[id];
+    for each (let addon in addons) {
       if (this.isAddonSyncable(addon)) {
         ids[addon.guid] = true;
       }
@@ -499,7 +474,7 @@ AddonsStore.prototype = {
       }
 
       this._log.info("Uninstalling add-on as part of wipe: " + addon.id);
-      Utils.catch.call(this, () => addon.uninstall())();
+      Utils.catch(addon.uninstall)();
     }
   },
 
@@ -538,22 +513,16 @@ AddonsStore.prototype = {
    *
    * @param  addon
    *         Addon instance
-   * @param ignoreRepoCheck
-   *         Should we skip checking the Addons repository (primarially useful
-   *         for testing and validation).
    * @return Boolean indicating whether it is appropriate for Sync
    */
-  isAddonSyncable: function isAddonSyncable(addon, ignoreRepoCheck = false) {
+  isAddonSyncable: function isAddonSyncable(addon) {
     // Currently, we limit syncable add-ons to those that are:
     //   1) In a well-defined set of types
     //   2) Installed in the current profile
     //   3) Not installed by a foreign entity (i.e. installed by the app)
     //      since they act like global extensions.
     //   4) Is not a hotfix.
-    //   5) The addons XPIProvider doesn't veto it (i.e not being installed in
-    //      the profile directory, or any other reasons it says the addon can't
-    //      be synced)
-    //   6) Are installed from AMO
+    //   5) Are installed from AMO
 
     // We could represent the test as a complex boolean expression. We go the
     // verbose route so the failure reason is logged.
@@ -573,12 +542,6 @@ AddonsStore.prototype = {
       return false;
     }
 
-    // If the addon manager says it's not syncable, we skip it.
-    if (!addon.isSyncable) {
-      this._log.debug(addon.id + " not syncable: vetoed by the addon manager.");
-      return false;
-    }
-
     // This may be too aggressive. If an add-on is downloaded from AMO and
     // manually placed in the profile directory, foreignInstall will be set.
     // Arguably, that add-on should be syncable.
@@ -589,20 +552,15 @@ AddonsStore.prototype = {
     }
 
     // Ignore hotfix extensions (bug 741670). The pref may not be defined.
-    // XXX - note that addon.isSyncable will be false for hotfix addons, so
-    // this check isn't strictly necessary - except for Sync tests which aren't
-    // setup to create a "real" hotfix addon. This can be removed once those
-    // tests are fixed (but keeping it doesn't hurt either)
     if (this._extensionsPrefs.get("hotfix.id", null) == addon.id) {
       this._log.debug(addon.id + " not syncable: is a hotfix.");
       return false;
     }
 
-    // If the AddonRepository's cache isn't enabled (which it typically isn't
-    // in tests), getCachedAddonByID always returns null - so skip the check
-    // in that case. We also provide a way to specifically opt-out of the check
-    // even if the cache is enabled, which is used by the validators.
-    if (ignoreRepoCheck || !AddonRepository.cacheEnabled) {
+    // We provide a back door to skip the repository checking of an add-on.
+    // This is utilized by the tests to make testing easier. Users could enable
+    // this, but it would sacrifice security.
+    if (Svc.Prefs.get("addons.ignoreRepositoryChecking", false)) {
       return true;
     }
 
@@ -745,69 +703,3 @@ AddonsTracker.prototype = {
     this.reconciler.stopListening();
   },
 };
-
-class AddonValidator extends CollectionValidator {
-  constructor(engine = null) {
-    super("addons", "id", [
-      "addonID",
-      "enabled",
-      "applicationID",
-      "source"
-    ]);
-    this.engine = engine;
-  }
-
-  getClientItems() {
-    return Promise.all([
-      new Promise(resolve =>
-        AddonManager.getAllAddons(resolve)),
-      new Promise(resolve =>
-        AddonManager.getAddonsWithOperationsByTypes(["extension", "theme"], resolve)),
-    ]).then(([installed, addonsWithPendingOperation]) => {
-      // Addons pending install won't be in the first list, but addons pending
-      // uninstall/enable/disable will be in both lists.
-      let all = new Map(installed.map(addon => [addon.id, addon]));
-      for (let addon of addonsWithPendingOperation) {
-        all.set(addon.id, addon);
-      }
-      // Convert to an array since Map.prototype.values returns an iterable
-      return [...all.values()];
-    });
-  }
-
-  normalizeClientItem(item) {
-    let enabled = !item.userDisabled;
-    if (item.pendingOperations & AddonManager.PENDING_ENABLE) {
-      enabled = true;
-    } else if (item.pendingOperations & AddonManager.PENDING_DISABLE) {
-      enabled = false;
-    }
-    return {
-      enabled,
-      id: item.syncGUID,
-      addonID: item.id,
-      applicationID: Services.appinfo.ID,
-      source: "amo", // check item.foreignInstall?
-      original: item
-    };
-  }
-
-  normalizeServerItem(item) {
-    let guid = this.engine._findDupe(item);
-    if (guid) {
-      item.id = guid;
-    }
-    return item;
-  }
-
-  clientUnderstands(item) {
-    return item.applicationID === Services.appinfo.ID;
-  }
-
-  syncedByClient(item) {
-    return !item.original.hidden &&
-           !item.original.isSystem &&
-           !(item.original.pendingOperations & AddonManager.PENDING_UNINSTALL) &&
-           this.engine.isAddonSyncable(item.original, true);
-  }
-}
diff --git a/services/sync/modules/engines/bookmarks.js b/services/sync/modules/engines/bookmarks.js
index 76a198a8b..1936afc3f 100644
--- a/services/sync/modules/engines/bookmarks.js
+++ b/services/sync/modules/engines/bookmarks.js
@@ -6,12 +6,11 @@ this.EXPORTED_SYMBOLS = ['BookmarksEngine', "PlacesItem", "Bookmark",
                          "BookmarkFolder", "BookmarkQuery",
                          "Livemark", "BookmarkSeparator"];
 
-var Cc = Components.classes;
-var Ci = Components.interfaces;
-var Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
 
 Cu.import("resource://gre/modules/PlacesUtils.jsm");
-Cu.import("resource://gre/modules/PlacesSyncUtils.jsm");
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://services-common/async.js");
 Cu.import("resource://services-sync/constants.js");
@@ -20,57 +19,21 @@ Cu.import("resource://services-sync/record.js");
 Cu.import("resource://services-sync/util.js");
 Cu.import("resource://gre/modules/Task.jsm");
 Cu.import("resource://gre/modules/PlacesBackups.jsm");
-XPCOMUtils.defineLazyModuleGetter(this, "BookmarkValidator",
-                                  "resource://services-sync/bookmark_validator.js");
-XPCOMUtils.defineLazyGetter(this, "PlacesBundle", () => {
-  let bundleService = Cc["@mozilla.org/intl/stringbundle;1"]
-                        .getService(Ci.nsIStringBundleService);
-  return bundleService.createBundle("chrome://places/locale/places.properties");
-});
-
-const ANNOS_TO_TRACK = [PlacesSyncUtils.bookmarks.DESCRIPTION_ANNO,
-                        PlacesSyncUtils.bookmarks.SIDEBAR_ANNO,
+
+const ALLBOOKMARKS_ANNO    = "AllBookmarks";
+const DESCRIPTION_ANNO     = "bookmarkProperties/description";
+const SIDEBAR_ANNO         = "bookmarkProperties/loadInSidebar";
+const MOBILEROOT_ANNO      = "mobile/bookmarksRoot";
+const MOBILE_ANNO          = "MobileBookmarks";
+const EXCLUDEBACKUP_ANNO   = "places/excludeFromBackup";
+const SMART_BOOKMARKS_ANNO = "Places/SmartBookmark";
+const PARENT_ANNO          = "sync/parent";
+const ORGANIZERQUERY_ANNO  = "PlacesOrganizer/OrganizerQuery";
+const ANNOS_TO_TRACK = [DESCRIPTION_ANNO, SIDEBAR_ANNO,
                         PlacesUtils.LMANNO_FEEDURI, PlacesUtils.LMANNO_SITEURI];
 
 const SERVICE_NOT_SUPPORTED = "Service not supported on this platform";
 const FOLDER_SORTINDEX = 1000000;
-const {
-  SOURCE_SYNC,
-  SOURCE_IMPORT,
-  SOURCE_IMPORT_REPLACE,
-} = Ci.nsINavBookmarksService;
-
-const SQLITE_MAX_VARIABLE_NUMBER = 999;
-
-const ORGANIZERQUERY_ANNO = "PlacesOrganizer/OrganizerQuery";
-const ALLBOOKMARKS_ANNO = "AllBookmarks";
-const MOBILE_ANNO = "MobileBookmarks";
-
-// The tracker ignores changes made by bookmark import and restore, and
-// changes made by Sync. We don't need to exclude `SOURCE_IMPORT`, but both
-// import and restore fire `bookmarks-restore-*` observer notifications, and
-// the tracker doesn't currently distinguish between the two.
-const IGNORED_SOURCES = [SOURCE_SYNC, SOURCE_IMPORT, SOURCE_IMPORT_REPLACE];
-
-// Returns the constructor for a bookmark record type.
-function getTypeObject(type) {
-  switch (type) {
-    case "bookmark":
-    case "microsummary":
-      return Bookmark;
-    case "query":
-      return BookmarkQuery;
-    case "folder":
-      return BookmarkFolder;
-    case "livemark":
-      return Livemark;
-    case "separator":
-      return BookmarkSeparator;
-    case "item":
-      return PlacesItem;
-  }
-  return null;
-}
 
 this.PlacesItem = function PlacesItem(collection, id, type) {
   CryptoWrapper.call(this, collection, id);
@@ -89,32 +52,26 @@ PlacesItem.prototype = {
   },
 
   getTypeObject: function PlacesItem_getTypeObject(type) {
-    let recordObj = getTypeObject(type);
-    if (!recordObj) {
-      throw new Error("Unknown places item object type: " + type);
+    switch (type) {
+      case "bookmark":
+      case "microsummary":
+        return Bookmark;
+      case "query":
+        return BookmarkQuery;
+      case "folder":
+        return BookmarkFolder;
+      case "livemark":
+        return Livemark;
+      case "separator":
+        return BookmarkSeparator;
+      case "item":
+        return PlacesItem;
     }
-    return recordObj;
+    throw "Unknown places item object type: " + type;
   },
 
   __proto__: CryptoWrapper.prototype,
   _logName: "Sync.Record.PlacesItem",
-
-  // Converts the record to a Sync bookmark object that can be passed to
-  // `PlacesSyncUtils.bookmarks.{insert, update}`.
-  toSyncBookmark() {
-    return {
-      kind: this.type,
-      syncId: this.id,
-      parentSyncId: this.parentid,
-    };
-  },
-
-  // Populates the record from a Sync bookmark object returned from
-  // `PlacesSyncUtils.bookmarks.fetch`.
-  fromSyncBookmark(item) {
-    this.parentid = item.parentSyncId;
-    this.parentName = item.parentTitle;
-  },
 };
 
 Utils.deferGetSet(PlacesItem,
@@ -127,27 +84,6 @@ this.Bookmark = function Bookmark(collection, id, type) {
 Bookmark.prototype = {
   __proto__: PlacesItem.prototype,
   _logName: "Sync.Record.Bookmark",
-
-  toSyncBookmark() {
-    let info = PlacesItem.prototype.toSyncBookmark.call(this);
-    info.title = this.title;
-    info.url = this.bmkUri;
-    info.description = this.description;
-    info.loadInSidebar = this.loadInSidebar;
-    info.tags = this.tags;
-    info.keyword = this.keyword;
-    return info;
-  },
-
-  fromSyncBookmark(item) {
-    PlacesItem.prototype.fromSyncBookmark.call(this, item);
-    this.title = item.title;
-    this.bmkUri = item.url.href;
-    this.description = item.description;
-    this.loadInSidebar = item.loadInSidebar;
-    this.tags = item.tags;
-    this.keyword = item.keyword;
-  },
 };
 
 Utils.deferGetSet(Bookmark,
@@ -161,19 +97,6 @@ this.BookmarkQuery = function BookmarkQuery(collection, id) {
 BookmarkQuery.prototype = {
   __proto__: Bookmark.prototype,
   _logName: "Sync.Record.BookmarkQuery",
-
-  toSyncBookmark() {
-    let info = Bookmark.prototype.toSyncBookmark.call(this);
-    info.folder = this.folderName;
-    info.query = this.queryId;
-    return info;
-  },
-
-  fromSyncBookmark(item) {
-    Bookmark.prototype.fromSyncBookmark.call(this, item);
-    this.folderName = item.folder;
-    this.queryId = item.query;
-  },
 };
 
 Utils.deferGetSet(BookmarkQuery,
@@ -186,20 +109,6 @@ this.BookmarkFolder = function BookmarkFolder(collection, id, type) {
 BookmarkFolder.prototype = {
   __proto__: PlacesItem.prototype,
   _logName: "Sync.Record.Folder",
-
-  toSyncBookmark() {
-    let info = PlacesItem.prototype.toSyncBookmark.call(this);
-    info.description = this.description;
-    info.title = this.title;
-    return info;
-  },
-
-  fromSyncBookmark(item) {
-    PlacesItem.prototype.fromSyncBookmark.call(this, item);
-    this.title = item.title;
-    this.description = item.description;
-    this.children = item.childSyncIds;
-  },
 };
 
 Utils.deferGetSet(BookmarkFolder, "cleartext", ["description", "title",
@@ -211,21 +120,6 @@ this.Livemark = function Livemark(collection, id) {
 Livemark.prototype = {
   __proto__: BookmarkFolder.prototype,
   _logName: "Sync.Record.Livemark",
-
-  toSyncBookmark() {
-    let info = BookmarkFolder.prototype.toSyncBookmark.call(this);
-    info.feed = this.feedUri;
-    info.site = this.siteUri;
-    return info;
-  },
-
-  fromSyncBookmark(item) {
-    BookmarkFolder.prototype.fromSyncBookmark.call(this, item);
-    this.feedUri = item.feed.href;
-    if (item.site) {
-      this.siteUri = item.site.href;
-    }
-  },
 };
 
 Utils.deferGetSet(Livemark, "cleartext", ["siteUri", "feedUri"]);
@@ -236,15 +130,81 @@ this.BookmarkSeparator = function BookmarkSeparator(collection, id) {
 BookmarkSeparator.prototype = {
   __proto__: PlacesItem.prototype,
   _logName: "Sync.Record.Separator",
-
-  fromSyncBookmark(item) {
-    PlacesItem.prototype.fromSyncBookmark.call(this, item);
-    this.pos = item.index;
-  },
 };
 
 Utils.deferGetSet(BookmarkSeparator, "cleartext", "pos");
 
+
+let kSpecialIds = {
+
+  // Special IDs. Note that mobile can attempt to create a record on
+  // dereference; special accessors are provided to prevent recursion within
+  // observers.
+  guids: ["menu", "places", "tags", "toolbar", "unfiled", "mobile"],
+
+  // Create the special mobile folder to store mobile bookmarks.
+  createMobileRoot: function createMobileRoot() {
+    let root = PlacesUtils.placesRootId;
+    let mRoot = PlacesUtils.bookmarks.createFolder(root, "mobile", -1);
+    PlacesUtils.annotations.setItemAnnotation(
+      mRoot, MOBILEROOT_ANNO, 1, 0, PlacesUtils.annotations.EXPIRE_NEVER);
+    PlacesUtils.annotations.setItemAnnotation(
+      mRoot, EXCLUDEBACKUP_ANNO, 1, 0, PlacesUtils.annotations.EXPIRE_NEVER);
+    return mRoot;
+  },
+
+  findMobileRoot: function findMobileRoot(create) {
+    // Use the (one) mobile root if it already exists.
+    let root = PlacesUtils.annotations.getItemsWithAnnotation(MOBILEROOT_ANNO, {});
+    if (root.length != 0)
+      return root[0];
+
+    if (create)
+      return this.createMobileRoot();
+
+    return null;
+  },
+
+  // Accessors for IDs.
+  isSpecialGUID: function isSpecialGUID(g) {
+    return this.guids.indexOf(g) != -1;
+  },
+
+  specialIdForGUID: function specialIdForGUID(guid, create) {
+    if (guid == "mobile") {
+      return this.findMobileRoot(create);
+    }
+    return this[guid];
+  },
+
+  // Don't bother creating mobile: if it doesn't exist, this ID can't be it!
+  specialGUIDForId: function specialGUIDForId(id) {
+    for each (let guid in this.guids)
+      if (this.specialIdForGUID(guid, false) == id)
+        return guid;
+    return null;
+  },
+
+  get menu() {
+    return PlacesUtils.bookmarksMenuFolderId;
+  },
+  get places() {
+    return PlacesUtils.placesRootId;
+  },
+  get tags() {
+    return PlacesUtils.tagsFolderId;
+  },
+  get toolbar() {
+    return PlacesUtils.toolbarFolderId;
+  },
+  get unfiled() {
+    return PlacesUtils.unfiledBookmarksFolderId;
+  },
+  get mobile() {
+    return this.findMobileRoot(true);
+  },
+};
+
 this.BookmarksEngine = function BookmarksEngine(service) {
   SyncEngine.call(this, "Bookmarks", service);
 }
@@ -257,103 +217,68 @@ BookmarksEngine.prototype = {
   _defaultSort: "index",
 
   syncPriority: 4,
-  allowSkippedRecord: false,
-
-  // A diagnostic helper to get the string value for a bookmark's URL given
-  // its ID. Always returns a string - on error will return a string in the
-  // form of "<description of error>" as this is purely for, eg, logging.
-  // (This means hitting the DB directly and we don't bother using a cached
-  // statement - we should rarely hit this.)
-  _getStringUrlForId(id) {
-    let url;
-    try {
-      let stmt = this._store._getStmt(`
-            SELECT h.url
-            FROM moz_places h
-            JOIN moz_bookmarks b ON h.id = b.fk
-            WHERE b.id = :id`);
-      stmt.params.id = id;
-      let rows = Async.querySpinningly(stmt, ["url"]);
-      url = rows.length == 0 ? "<not found>" : rows[0].url;
-    } catch (ex) {
-      if (Async.isShutdownException(ex)) {
-        throw ex;
-      }
-      if (ex instanceof Ci.mozIStorageError) {
-        url = `<failed: Storage error: ${ex.message} (${ex.result})>`;
-      } else {
-        url = `<failed: ${ex.toString()}>`;
-      }
-    }
-    return url;
-  },
 
-  _guidMapFailed: false,
-  _buildGUIDMap: function _buildGUIDMap() {
-    let store = this._store;
-    let guidMap = {};
-    let tree = Async.promiseSpinningly(PlacesUtils.promiseBookmarksTree("", {
-      includeItemIds: true
-    }));
-    function* walkBookmarksTree(tree, parent=null) {
-      if (tree) {
-        // Skip root node
-        if (parent) {
-          yield [tree, parent];
+  _sync: function _sync() {
+    let engine = this;
+    let batchEx = null;
+
+    // Try running sync in batch mode
+    PlacesUtils.bookmarks.runInBatchMode({
+      runBatched: function wrappedSync() {
+        try {
+          SyncEngine.prototype._sync.call(engine);
         }
-        if (tree.children) {
-          for (let child of tree.children) {
-            store._sleep(0); // avoid jank while looping.
-            yield* walkBookmarksTree(child, tree);
-          }
+        catch(ex) {
+          batchEx = ex;
         }
       }
-    }
+    }, null);
 
-    function* walkBookmarksRoots(tree, rootIDs) {
-      for (let id of rootIDs) {
-        let bookmarkRoot = tree.children.find(child => child.id === id);
-        if (bookmarkRoot === null) {
-          continue;
-        }
-        yield* walkBookmarksTree(bookmarkRoot, tree);
-      }
+    // Expose the exception if something inside the batch failed
+    if (batchEx != null) {
+      throw batchEx;
     }
+  },
 
-    let rootsToWalk = getChangeRootIds();
-
-    for (let [node, parent] of walkBookmarksRoots(tree, rootsToWalk)) {
-      let {guid, id, type: placeType} = node;
-      guid = PlacesSyncUtils.bookmarks.guidToSyncId(guid);
+  _guidMapFailed: false,
+  _buildGUIDMap: function _buildGUIDMap() {
+    let guidMap = {};
+    for (let guid in this._store.getAllIDs()) {
+      // Figure out with which key to store the mapping.
       let key;
-      switch (placeType) {
-        case PlacesUtils.TYPE_X_MOZ_PLACE:
-          // Bookmark
-          let query = null;
-          if (node.annos && node.uri.startsWith("place:")) {
-            query = node.annos.find(({name}) =>
-              name === PlacesSyncUtils.bookmarks.SMART_BOOKMARKS_ANNO);
-          }
-          if (query && query.value) {
-            key = "q" + query.value;
-          } else {
-            key = "b" + node.uri + ":" + (node.title || "");
-          }
+      let id = this._store.idForGUID(guid);
+      switch (PlacesUtils.bookmarks.getItemType(id)) {
+        case PlacesUtils.bookmarks.TYPE_BOOKMARK:
+
+          // Smart bookmarks map to their annotation value.
+          let queryId;
+          try {
+            queryId = PlacesUtils.annotations.getItemAnnotation(
+              id, SMART_BOOKMARKS_ANNO);
+          } catch(ex) {}
+          
+          if (queryId)
+            key = "q" + queryId;
+          else
+            key = "b" + PlacesUtils.bookmarks.getBookmarkURI(id).spec + ":" +
+                  PlacesUtils.bookmarks.getItemTitle(id);
           break;
-        case PlacesUtils.TYPE_X_MOZ_PLACE_CONTAINER:
-          // Folder
-          key = "f" + (node.title || "");
+        case PlacesUtils.bookmarks.TYPE_FOLDER:
+          key = "f" + PlacesUtils.bookmarks.getItemTitle(id);
           break;
-        case PlacesUtils.TYPE_X_MOZ_PLACE_SEPARATOR:
-          // Separator
-          key = "s" + node.index;
+        case PlacesUtils.bookmarks.TYPE_SEPARATOR:
+          key = "s" + PlacesUtils.bookmarks.getItemIndex(id);
           break;
         default:
-          this._log.error("Unknown place type: '"+placeType+"'");
           continue;
       }
 
-      let parentName = parent.title || "";
+      // The mapping is on a per parent-folder-name basis.
+      let parent = PlacesUtils.bookmarks.getFolderIdForItem(id);
+      if (parent <= 0)
+        continue;
+
+      let parentName = PlacesUtils.bookmarks.getItemTitle(parent);
       if (guidMap[parentName] == null)
         guidMap[parentName] = {};
 
@@ -381,17 +306,17 @@ BookmarksEngine.prototype = {
         // hack should get them to dupe correctly.
         if (item.queryId) {
           key = "q" + item.queryId;
-          altKey = "b" + item.bmkUri + ":" + (item.title || "");
+          altKey = "b" + item.bmkUri + ":" + item.title;
           break;
         }
         // No queryID? Fall through to the regular bookmark case.
       case "bookmark":
       case "microsummary":
-        key = "b" + item.bmkUri + ":" + (item.title || "");
+        key = "b" + item.bmkUri + ":" + item.title;
         break;
       case "folder":
       case "livemark":
-        key = "f" + (item.title || "");
+        key = "f" + item.title;
         break;
       case "separator":
         key = "s" + item.pos;
@@ -405,22 +330,21 @@ BookmarksEngine.prototype = {
     let guidMap = this._guidMap;
 
     // Give the GUID if we have the matching pair.
-    let parentName = item.parentName || "";
-    this._log.trace("Finding mapping: " + parentName + ", " + key);
-    let parent = guidMap[parentName];
-
+    this._log.trace("Finding mapping: " + item.parentName + ", " + key);
+    let parent = guidMap[item.parentName];
+    
     if (!parent) {
       this._log.trace("No parent => no dupe.");
       return undefined;
     }
-
+      
     let dupe = parent[key];
-
+    
     if (dupe) {
       this._log.trace("Mapped dupe: " + dupe);
       return dupe;
     }
-
+    
     if (altKey) {
       dupe = parent[altKey];
       if (dupe) {
@@ -428,7 +352,7 @@ BookmarksEngine.prototype = {
         return dupe;
       }
     }
-
+    
     this._log.trace("No dupe found for key " + key + "/" + altKey + ".");
     return undefined;
   },
@@ -437,7 +361,7 @@ BookmarksEngine.prototype = {
     SyncEngine.prototype._syncStartup.call(this);
 
     let cb = Async.makeSpinningCallback();
-    Task.spawn(function* () {
+    Task.spawn(function() {
       // For first-syncs, make a backup for the user to restore
       if (this.lastSync == 0) {
         this._log.debug("Bookmarks backup starting.");
@@ -449,7 +373,8 @@ BookmarksEngine.prototype = {
         // Failure to create a backup is somewhat bad, but probably not bad
         // enough to prevent syncing of bookmarks - so just log the error and
         // continue.
-        this._log.warn("Error while backing up bookmarks, but continuing with sync", ex);
+        this._log.warn("Got exception \"" + Utils.exceptionStr(ex) +
+                       "\" backing up bookmarks, but continuing with sync.");
         cb();
       }
     );
@@ -464,10 +389,9 @@ BookmarksEngine.prototype = {
       try {
         guidMap = this._buildGUIDMap();
       } catch (ex) {
-        if (Async.isShutdownException(ex)) {
-          throw ex;
-        }
-        this._log.warn("Error while building GUID map, skipping all other incoming items", ex);
+        this._log.warn("Got exception \"" + Utils.exceptionStr(ex) +
+                       "\" building GUID map." +
+                       " Skipping all other incoming items.");
         throw {code: Engine.prototype.eEngineAbortApplyIncoming,
                cause: ex};
       }
@@ -476,71 +400,17 @@ BookmarksEngine.prototype = {
     });
 
     this._store._childrenToOrder = {};
-    this._store.clearPendingDeletions();
-  },
-
-  _deletePending() {
-    // Delete pending items -- See the comment above BookmarkStore's deletePending
-    let newlyModified = Async.promiseSpinningly(this._store.deletePending());
-    let now = this._tracker._now();
-    this._log.debug("Deleted pending items", newlyModified);
-    for (let modifiedSyncID of newlyModified) {
-      if (!this._modified.has(modifiedSyncID)) {
-        this._modified.set(modifiedSyncID, { timestamp: now, deleted: false });
-      }
-    }
-  },
-
-  // We avoid reviving folders since reviving them properly would require
-  // reviving their children as well. Unfortunately, this is the wrong choice
-  // in the case of a bookmark restore where wipeServer failed -- if the
-  // server has the folder as deleted, we *would* want to reupload this folder.
-  // This is mitigated by the fact that we move any undeleted children to the
-  // grandparent when deleting the parent.
-  _shouldReviveRemotelyDeletedRecord(item) {
-    let kind = Async.promiseSpinningly(
-      PlacesSyncUtils.bookmarks.getKindForSyncId(item.id));
-    if (kind === PlacesSyncUtils.bookmarks.KINDS.FOLDER) {
-      return false;
-    }
-
-    // In addition to preventing the deletion of this record (handled by the caller),
-    // we need to mark the parent of this record for uploading next sync, in order
-    // to ensure its children array is accurate.
-    let modifiedTimestamp = this._modified.getModifiedTimestamp(item.id);
-    if (!modifiedTimestamp) {
-      // We only expect this to be called with items locally modified, so
-      // something strange is going on - play it safe and don't revive it.
-      this._log.error("_shouldReviveRemotelyDeletedRecord called on unmodified item: " + item.id);
-      return false;
-    }
-
-    let localID = this._store.idForGUID(item.id);
-    let localParentID = PlacesUtils.bookmarks.getFolderIdForItem(localID);
-    let localParentSyncID = this._store.GUIDForId(localParentID);
-
-    this._log.trace(`Reviving item "${item.id}" and marking parent ${localParentSyncID} as modified.`);
-
-    if (!this._modified.has(localParentSyncID)) {
-      this._modified.set(localParentSyncID, {
-        timestamp: modifiedTimestamp,
-        deleted: false
-      });
-    }
-    return true
   },
 
   _processIncoming: function (newitems) {
     try {
       SyncEngine.prototype._processIncoming.call(this, newitems);
     } finally {
-      try {
-        this._deletePending();
-      } finally {
-        // Reorder children.
-        this._store._orderChildren();
-        delete this._store._childrenToOrder;
-      }
+      // Reorder children.
+      this._tracker.ignoreAll = true;
+      this._store._orderChildren();
+      this._tracker.ignoreAll = false;
+      delete this._store._childrenToOrder;
     }
   },
 
@@ -575,154 +445,16 @@ BookmarksEngine.prototype = {
     }
     let mapped = this._mapDupe(item);
     this._log.debug(item.id + " mapped to " + mapped);
-    // We must return a string, not an object, and the entries in the GUIDMap
-    // are created via "new String()" making them an object.
-    return mapped ? mapped.toString() : mapped;
-  },
-
-  pullAllChanges() {
-    return new BookmarksChangeset(this._store.getAllIDs());
-  },
-
-  pullNewChanges() {
-    let modifiedGUIDs = this._getModifiedGUIDs();
-    if (!modifiedGUIDs.length) {
-      return new BookmarksChangeset(this._tracker.changedIDs);
-    }
-
-    // We don't use `PlacesUtils.promiseDBConnection` here because
-    // `getChangedIDs` might be called while we're in a batch, meaning we
-    // won't see any changes until the batch finishes and the transaction
-    // commits.
-    let db = PlacesUtils.history.QueryInterface(Ci.nsPIPlacesDatabase)
-                        .DBConnection;
-
-    // Filter out tags, organizer queries, and other descendants that we're
-    // not tracking. We chunk `modifiedGUIDs` because SQLite limits the number
-    // of bound parameters per query.
-    for (let startIndex = 0;
-         startIndex < modifiedGUIDs.length;
-         startIndex += SQLITE_MAX_VARIABLE_NUMBER) {
-
-      let chunkLength = Math.min(SQLITE_MAX_VARIABLE_NUMBER,
-                                 modifiedGUIDs.length - startIndex);
-
-      let query = `
-        WITH RECURSIVE
-        modifiedGuids(guid) AS (
-          VALUES ${new Array(chunkLength).fill("(?)").join(", ")}
-        ),
-        syncedItems(id) AS (
-          VALUES ${getChangeRootIds().map(id => `(${id})`).join(", ")}
-          UNION ALL
-          SELECT b.id
-          FROM moz_bookmarks b
-          JOIN syncedItems s ON b.parent = s.id
-        )
-        SELECT b.guid
-        FROM modifiedGuids m
-        JOIN moz_bookmarks b ON b.guid = m.guid
-        LEFT JOIN syncedItems s ON b.id = s.id
-        WHERE s.id IS NULL
-      `;
-
-      let statement = db.createAsyncStatement(query);
-      try {
-        for (let i = 0; i < chunkLength; i++) {
-          statement.bindByIndex(i, modifiedGUIDs[startIndex + i]);
-        }
-        let results = Async.querySpinningly(statement, ["guid"]);
-        for (let { guid } of results) {
-          let syncID = PlacesSyncUtils.bookmarks.guidToSyncId(guid);
-          this._tracker.removeChangedID(syncID);
-        }
-      } finally {
-        statement.finalize();
-      }
-    }
-
-    return new BookmarksChangeset(this._tracker.changedIDs);
-  },
-
-  // Returns an array of Places GUIDs for all changed items. Ignores deletions,
-  // which won't exist in the DB and shouldn't be removed from the tracker.
-  _getModifiedGUIDs() {
-    let guids = [];
-    for (let syncID in this._tracker.changedIDs) {
-      if (this._tracker.changedIDs[syncID].deleted === true) {
-        // The `===` check also filters out old persisted timestamps,
-        // which won't have a `deleted` property.
-        continue;
-      }
-      let guid = PlacesSyncUtils.bookmarks.syncIdToGuid(syncID);
-      guids.push(guid);
-    }
-    return guids;
-  },
-
-  // Called when _findDupe returns a dupe item and the engine has decided to
-  // switch the existing item to the new incoming item.
-  _switchItemToDupe(localDupeGUID, incomingItem) {
-    // We unconditionally change the item's ID in case the engine knows of
-    // an item but doesn't expose it through itemExists. If the API
-    // contract were stronger, this could be changed.
-    this._log.debug("Switching local ID to incoming: " + localDupeGUID + " -> " +
-                    incomingItem.id);
-    this._store.changeItemID(localDupeGUID, incomingItem.id);
-
-    // And mark the parent as being modified. Given we de-dupe based on the
-    // parent *name* it's possible the item having its GUID changed has a
-    // different parent from the incoming record.
-    // So we need to find the GUID of the local parent.
-    let now = this._tracker._now();
-    let localID = this._store.idForGUID(incomingItem.id);
-    let localParentID = PlacesUtils.bookmarks.getFolderIdForItem(localID);
-    let localParentGUID = this._store.GUIDForId(localParentID);
-    this._modified.set(localParentGUID, { modified: now, deleted: false });
-
-    // And we also add the parent as reflected in the incoming record as the
-    // de-dupe process might have used an existing item in a different folder.
-    // But only if the parent exists, otherwise we will upload a deleted item
-    // when it might actually be valid, just unknown to us. Note that this
-    // scenario will still leave us with inconsistent client and server states;
-    // the incoming record on the server references a parent that isn't the
-    // actual parent locally - see bug 1297955.
-    if (localParentGUID != incomingItem.parentid) {
-      let remoteParentID = this._store.idForGUID(incomingItem.parentid);
-      if (remoteParentID > 0) {
-        // The parent specified in the record does exist, so we are going to
-        // attempt a move when we come to applying the record. Mark the parent
-        // as being modified so we will later upload it with the new child
-        // reference.
-        this._modified.set(incomingItem.parentid, { modified: now, deleted: false });
-      } else {
-        // We aren't going to do a move as we don't have the parent (yet?).
-        // When applying the record we will add our special PARENT_ANNO
-        // annotation, so if it arrives in the future (either this Sync or a
-        // later one) it will be reparented.
-        this._log.debug(`Incoming duplicate item ${incomingItem.id} specifies ` +
-                        `non-existing parent ${incomingItem.parentid}`);
-      }
-    }
-
-    // The local, duplicate ID is always deleted on the server - but for
-    // bookmarks it is a logical delete.
-    // Simply adding this (now non-existing) ID to the tracker is enough.
-    this._modified.set(localDupeGUID, { modified: now, deleted: true });
-  },
-  getValidator() {
-    return new BookmarkValidator();
+    return mapped;
   }
 };
 
 function BookmarksStore(name, engine) {
   Store.call(this, name, engine);
-  this._foldersToDelete = new Set();
-  this._atomsToDelete = new Set();
+
   // Explicitly nullify our references to our cached services so we don't leak
   Svc.Obs.add("places-shutdown", function() {
-    for (let query in this._stmts) {
-      let stmt = this._stmts[query];
+    for each (let [query, stmt] in Iterator(this._stmts)) {
       stmt.finalize();
     }
     this._stmts = {};
@@ -732,12 +464,70 @@ BookmarksStore.prototype = {
   __proto__: Store.prototype,
 
   itemExists: function BStore_itemExists(id) {
-    return this.idForGUID(id) > 0;
+    return this.idForGUID(id, true) > 0;
   },
+  
+  /*
+   * If the record is a tag query, rewrite it to refer to the local tag ID.
+   * 
+   * Otherwise, just return.
+   */
+  preprocessTagQuery: function preprocessTagQuery(record) {
+    if (record.type != "query" ||
+        record.bmkUri == null ||
+        !record.folderName)
+      return;
+    
+    // Yes, this works without chopping off the "place:" prefix.
+    let uri           = record.bmkUri
+    let queriesRef    = {};
+    let queryCountRef = {};
+    let optionsRef    = {};
+    PlacesUtils.history.queryStringToQueries(uri, queriesRef, queryCountRef,
+                                             optionsRef);
+    
+    // We only process tag URIs.
+    if (optionsRef.value.resultType != optionsRef.value.RESULTS_AS_TAG_CONTENTS)
+      return;
+    
+    // Tag something to ensure that the tag exists.
+    let tag = record.folderName;
+    let dummyURI = Utils.makeURI("about:weave#BStore_preprocess");
+    PlacesUtils.tagging.tagURI(dummyURI, [tag]);
+
+    // Look for the id of the tag, which might just have been added.
+    let tags = this._getNode(PlacesUtils.tagsFolderId);
+    if (!(tags instanceof Ci.nsINavHistoryQueryResultNode)) {
+      this._log.debug("tags isn't an nsINavHistoryQueryResultNode; aborting.");
+      return;
+    }
 
+    tags.containerOpen = true;
+    try {
+      for (let i = 0; i < tags.childCount; i++) {
+        let child = tags.getChild(i);
+        if (child.title == tag) {
+          // Found the tag, so fix up the query to use the right id.
+          this._log.debug("Tag query folder: " + tag + " = " + child.itemId);
+          
+          this._log.trace("Replacing folders in: " + uri);
+          for each (let q in queriesRef.value)
+            q.setFolders([child.itemId], 1);
+          
+          record.bmkUri = PlacesUtils.history.queriesToQueryString(
+            queriesRef.value, queryCountRef.value, optionsRef.value);
+          return;
+        }
+      }
+    }
+    finally {
+      tags.containerOpen = false;
+    }
+  },
+  
   applyIncoming: function BStore_applyIncoming(record) {
     this._log.debug("Applying record " + record.id);
-    let isSpecial = PlacesSyncUtils.bookmarks.ROOTS.includes(record.id);
+    let isSpecial = record.id in kSpecialIds;
 
     if (record.deleted) {
       if (isSpecial) {
@@ -765,217 +555,548 @@ BookmarksStore.prototype = {
       return;
     }
 
+    // Preprocess the record before doing the normal apply.
+    this.preprocessTagQuery(record);
+
     // Figure out the local id of the parent GUID if available
     let parentGUID = record.parentid;
     if (!parentGUID) {
       throw "Record " + record.id + " has invalid parentid: " + parentGUID;
     }
-    this._log.debug("Remote parent is " + parentGUID);
+    this._log.debug("Local parent is " + parentGUID);
+
+    let parentId = this.idForGUID(parentGUID);
+    if (parentId > 0) {
+      // Save the parent id for modifying the bookmark later
+      record._parent = parentId;
+      record._orphan = false;
+      this._log.debug("Record " + record.id + " is not an orphan.");
+    } else {
+      this._log.trace("Record " + record.id +
+                      " is an orphan: could not find parent " + parentGUID);
+      record._orphan = true;
+    }
 
     // Do the normal processing of incoming records
     Store.prototype.applyIncoming.call(this, record);
 
-    if (record.type == "folder" && record.children) {
-      this._childrenToOrder[record.id] = record.children;
+    // Do some post-processing if we have an item
+    let itemId = this.idForGUID(record.id);
+    if (itemId > 0) {
+      // Move any children that are looking for this folder as a parent
+      if (record.type == "folder") {
+        this._reparentOrphans(itemId);
+        // Reorder children later
+        if (record.children)
+          this._childrenToOrder[record.id] = record.children;
+      }
+
+      // Create an annotation to remember that it needs reparenting.
+      if (record._orphan) {
+        PlacesUtils.annotations.setItemAnnotation(
+          itemId, PARENT_ANNO, parentGUID, 0,
+          PlacesUtils.annotations.EXPIRE_NEVER);
+      }
+    }
+  },
+
+  /**
+   * Find all ids of items that have a given value for an annotation
+   */
+  _findAnnoItems: function BStore__findAnnoItems(anno, val) {
+    return PlacesUtils.annotations.getItemsWithAnnotation(anno, {})
+                      .filter(function(id) {
+      return PlacesUtils.annotations.getItemAnnotation(id, anno) == val;
+    });
+  },
+
+  /**
+   * For the provided parent item, attach its children to it
+   */
+  _reparentOrphans: function _reparentOrphans(parentId) {
+    // Find orphans and reunite with this folder parent
+    let parentGUID = this.GUIDForId(parentId);
+    let orphans = this._findAnnoItems(PARENT_ANNO, parentGUID);
+
+    this._log.debug("Reparenting orphans " + orphans + " to " + parentId);
+    orphans.forEach(function(orphan) {
+      // Move the orphan to the parent and drop the missing parent annotation
+      if (this._reparentItem(orphan, parentId)) {
+        PlacesUtils.annotations.removeItemAnnotation(orphan, PARENT_ANNO);
+      }
+    }, this);
+  },
+
+  _reparentItem: function _reparentItem(itemId, parentId) {
+    this._log.trace("Attempting to move item " + itemId + " to new parent " +
+                    parentId);
+    try {
+      if (parentId > 0) {
+        PlacesUtils.bookmarks.moveItem(itemId, parentId,
+                                       PlacesUtils.bookmarks.DEFAULT_INDEX);
+        return true;
+      }
+    } catch(ex) {
+      this._log.debug("Failed to reparent item. " + Utils.exceptionStr(ex));
+    }
+    return false;
+  },
+
+  // Turn a record's nsINavBookmarksService constant and other attributes into
+  // a granular type for comparison.
+  _recordType: function _recordType(itemId) {
+    let bms  = PlacesUtils.bookmarks;
+    let type = bms.getItemType(itemId);
+
+    switch (type) {
+      case bms.TYPE_FOLDER:
+        if (PlacesUtils.annotations
+                       .itemHasAnnotation(itemId, PlacesUtils.LMANNO_FEEDURI)) {
+          return "livemark";
+        }
+        return "folder";
+
+      case bms.TYPE_BOOKMARK:
+        let bmkUri = bms.getBookmarkURI(itemId).spec;
+        if (bmkUri.indexOf("place:") == 0) {
+          return "query";
+        }
+        return "bookmark";
+
+      case bms.TYPE_SEPARATOR:
+        return "separator";
+
+      default:
+        return null;
     }
   },
 
   create: function BStore_create(record) {
-    let info = record.toSyncBookmark();
-    // This can throw if we're inserting an invalid or incomplete bookmark.
-    // That's fine; the exception will be caught by `applyIncomingBatch`
-    // without aborting further processing.
-    let item = Async.promiseSpinningly(PlacesSyncUtils.bookmarks.insert(info));
-    if (item) {
-      this._log.debug(`Created ${item.kind} ${item.syncId} under ${
-        item.parentSyncId}`, item);
+    // Default to unfiled if we don't have the parent yet.
+    
+    // Valid parent IDs are all positive integers. Other values -- undefined,
+    // null, -1 -- all compare false for > 0, so this catches them all. We
+    // don't just use <= without the !, because undefined and null compare
+    // false for that, too!
+    if (!(record._parent > 0)) {
+      this._log.debug("Parent is " + record._parent + "; reparenting to unfiled.");
+      record._parent = kSpecialIds.unfiled;
+    }
+
+    let newId;
+    switch (record.type) {
+    case "bookmark":
+    case "query":
+    case "microsummary": {
+      let uri = Utils.makeURI(record.bmkUri);
+      newId = PlacesUtils.bookmarks.insertBookmark(
+        record._parent, uri, PlacesUtils.bookmarks.DEFAULT_INDEX, record.title);
+      this._log.debug("created bookmark " + newId + " under " + record._parent
+                      + " as " + record.title + " " + record.bmkUri);
+
+      // Smart bookmark annotations are strings.
+      if (record.queryId) {
+        PlacesUtils.annotations.setItemAnnotation(
+          newId, SMART_BOOKMARKS_ANNO, record.queryId, 0,
+          PlacesUtils.annotations.EXPIRE_NEVER);
+      }
+
+      if (Array.isArray(record.tags)) {
+        this._tagURI(uri, record.tags);
+      }
+      PlacesUtils.bookmarks.setKeywordForBookmark(newId, record.keyword);
+      if (record.description) {
+        PlacesUtils.annotations.setItemAnnotation(
+          newId, DESCRIPTION_ANNO, record.description, 0,
+          PlacesUtils.annotations.EXPIRE_NEVER);
+      }
+
+      if (record.loadInSidebar) {
+        PlacesUtils.annotations.setItemAnnotation(
+          newId, SIDEBAR_ANNO, true, 0,
+          PlacesUtils.annotations.EXPIRE_NEVER);
+      }
+
+    } break;
+    case "folder":
+      newId = PlacesUtils.bookmarks.createFolder(
+        record._parent, record.title, PlacesUtils.bookmarks.DEFAULT_INDEX);
+      this._log.debug("created folder " + newId + " under " + record._parent
+                      + " as " + record.title);
+
+      if (record.description) {
+        PlacesUtils.annotations.setItemAnnotation(
+          newId, DESCRIPTION_ANNO, record.description, 0,
+          PlacesUtils.annotations.EXPIRE_NEVER);
+      }
+
+      // record.children will be dealt with in _orderChildren.
+      break;
+    case "livemark":
+      let siteURI = null;
+      if (!record.feedUri) {
+        this._log.debug("No feed URI: skipping livemark record " + record.id);
+        return;
+      }
+      if (PlacesUtils.annotations
+                     .itemHasAnnotation(record._parent, PlacesUtils.LMANNO_FEEDURI)) {
+        this._log.debug("Invalid parent: skipping livemark record " + record.id);
+        return;
+      }
+
+      if (record.siteUri != null)
+        siteURI = Utils.makeURI(record.siteUri);
+
+      // Until this engine can handle asynchronous error reporting, we need to
+      // detect errors on creation synchronously.
+      let spinningCb = Async.makeSpinningCallback();
+
+      let livemarkObj = {title: record.title,
+                         parentId: record._parent,
+                         index: PlacesUtils.bookmarks.DEFAULT_INDEX,
+                         feedURI: Utils.makeURI(record.feedUri),
+                         siteURI: siteURI,
+                         guid: record.id};
+      PlacesUtils.livemarks.addLivemark(livemarkObj).then(
+        aLivemark => { spinningCb(null, [Components.results.NS_OK, aLivemark]) },
+        () => { spinningCb(null, [Components.results.NS_ERROR_UNEXPECTED, aLivemark]) }
+      );
+
+      let [status, livemark] = spinningCb.wait();
+      if (!Components.isSuccessCode(status)) {
+        throw status;
+      }
+
+      this._log.debug("Created livemark " + livemark.id + " under " +
+                      livemark.parentId + " as " + livemark.title +
+                      ", " + livemark.siteURI.spec + ", " +
+                      livemark.feedURI.spec + ", GUID " +
+                      livemark.guid);
+      break;
+    case "separator":
+      newId = PlacesUtils.bookmarks.insertSeparator(
+        record._parent, PlacesUtils.bookmarks.DEFAULT_INDEX);
+      this._log.debug("created separator " + newId + " under " + record._parent);
+      break;
+    case "item":
+      this._log.debug(" -> got a generic places item.. do nothing?");
+      return;
+    default:
+      this._log.error("_create: Unknown item type: " + record.type);
+      return;
+    }
+
+    if (newId) {
+      // Livemarks can set the GUID through the API, so there's no need to
+      // do that here.
+      this._log.trace("Setting GUID of new item " + newId + " to " + record.id);
+      this._setGUID(newId, record.id);
+    }
+  },
+
+  // Factored out of `remove` to avoid redundant DB queries when the Places ID
+  // is already known.
+  removeById: function removeById(itemId, guid) {
+    let type = PlacesUtils.bookmarks.getItemType(itemId);
+
+    switch (type) {
+    case PlacesUtils.bookmarks.TYPE_BOOKMARK:
+      this._log.debug("  -> removing bookmark " + guid);
+      PlacesUtils.bookmarks.removeItem(itemId);
+      break;
+    case PlacesUtils.bookmarks.TYPE_FOLDER:
+      this._log.debug("  -> removing folder " + guid);
+      PlacesUtils.bookmarks.removeItem(itemId);
+      break;
+    case PlacesUtils.bookmarks.TYPE_SEPARATOR:
+      this._log.debug("  -> removing separator " + guid);
+      PlacesUtils.bookmarks.removeItem(itemId);
+      break;
+    default:
+      this._log.error("remove: Unknown item type: " + type);
+      break;
     }
   },
 
   remove: function BStore_remove(record) {
-    if (PlacesSyncUtils.bookmarks.isRootSyncID(record.id)) {
+    if (kSpecialIds.isSpecialGUID(record.id)) {
       this._log.warn("Refusing to remove special folder " + record.id);
       return;
     }
-    let recordKind = Async.promiseSpinningly(
-      PlacesSyncUtils.bookmarks.getKindForSyncId(record.id));
-    let isFolder = recordKind === PlacesSyncUtils.bookmarks.KINDS.FOLDER;
-    this._log.trace(`Buffering removal of item "${record.id}" of type "${recordKind}".`);
-    if (isFolder) {
-      this._foldersToDelete.add(record.id);
-    } else {
-      this._atomsToDelete.add(record.id);
+
+    let itemId = this.idForGUID(record.id);
+    if (itemId <= 0) {
+      this._log.debug("Item " + record.id + " already removed");
+      return;
     }
+    this.removeById(itemId, record.id);
   },
 
-  update: function BStore_update(record) {
-    let info = record.toSyncBookmark();
-    let item = Async.promiseSpinningly(PlacesSyncUtils.bookmarks.update(info));
-    if (item) {
-      this._log.debug(`Updated ${item.kind} ${item.syncId} under ${
-        item.parentSyncId}`, item);
-    }
+  _taggableTypes: ["bookmark", "microsummary", "query"],
+  isTaggable: function isTaggable(recordType) {
+    return this._taggableTypes.indexOf(recordType) != -1;
   },
 
-  _orderChildren: function _orderChildren() {
-    let promises = Object.keys(this._childrenToOrder).map(syncID => {
-      let children = this._childrenToOrder[syncID];
-      return PlacesSyncUtils.bookmarks.order(syncID, children).catch(ex => {
-        this._log.debug(`Could not order children for ${syncID}`, ex);
-      });
-    });
-    Async.promiseSpinningly(Promise.all(promises));
-  },
-
-  // There's some complexity here around pending deletions. Our goals:
-  //
-  // - Don't delete any bookmarks a user has created but not explicitly deleted
-  //   (This includes any bookmark that was not a child of the folder at the
-  //   time the deletion was recorded, and also bookmarks restored from a backup).
-  // - Don't undelete any bookmark without ensuring the server structure
-  //   includes it (see `BookmarkEngine.prototype._shouldReviveRemotelyDeletedRecord`)
-  //
-  // This leads the following approach:
-  //
-  // - Additions, moves, and updates are processed before deletions.
-  //     - To do this, all deletion operations are buffered during a sync. Folders
-  //       we plan on deleting have their sync id's stored in `this._foldersToDelete`,
-  //       and non-folders we plan on deleting have their sync id's stored in
-  //       `this._atomsToDelete`.
-  //     - The exception to this is the moves that occur to fix the order of bookmark
-  //       children, which are performed after we process deletions.
-  // - Non-folders are deleted before folder deletions, so that when we process
-  //   folder deletions we know the correct state.
-  // - Remote deletions always win for folders, but do not result in recursive
-  //   deletion of children. This is a hack because we're not able to distinguish
-  //   between value changes and structural changes to folders, and we don't even
-  //   have the old server record to compare to. See `BookmarkEngine`'s
-  //   `_shouldReviveRemotelyDeletedRecord` method.
-  // - When a folder is deleted, its remaining children are moved in order to
-  //   their closest living ancestor.  If this is interrupted (unlikely, but
-  //   possible given that we don't perform this operation in a transaction),
-  //   we revive the folder.
-  // - Remote deletions can lose for non-folders, but only until we handle
-  //   bookmark restores correctly (removing stale state from the server -- this
-  //   is to say, if bug 1230011 is fixed, we should never revive bookmarks).
-
-  deletePending: Task.async(function* deletePending() {
-    yield this._deletePendingAtoms();
-    let guidsToUpdate = yield this._deletePendingFolders();
-    this.clearPendingDeletions();
-    return guidsToUpdate;
-  }),
-
-  clearPendingDeletions() {
-    this._foldersToDelete.clear();
-    this._atomsToDelete.clear();
-  },
-
-  _deleteAtom: Task.async(function* _deleteAtom(syncID) {
-    try {
-      let info = yield PlacesSyncUtils.bookmarks.remove(syncID, {
-        preventRemovalOfNonEmptyFolders: true
-      });
-      this._log.trace(`Removed item ${syncID} with type ${info.type}`);
-    } catch (ex) {
-      // Likely already removed.
-      this._log.trace(`Error removing ${syncID}`, ex);
+  update: function BStore_update(record) {
+    let itemId = this.idForGUID(record.id);
+
+    if (itemId <= 0) {
+      this._log.debug("Skipping update for unknown item: " + record.id);
+      return;
     }
-  }),
-
-  _deletePendingAtoms() {
-    return Promise.all(
-      [...this._atomsToDelete.values()]
-        .map(syncID => this._deleteAtom(syncID)));
-  },
-
-  // Returns an array of sync ids that need updates.
-  _deletePendingFolders: Task.async(function* _deletePendingFolders() {
-    // To avoid data loss, we don't want to just delete the folder outright,
-    // so we buffer folder deletions and process them at the end (now).
-    //
-    // At this point, any member in the folder that remains is either a folder
-    // pending deletion (which we'll get to in this function), or an item that
-    // should not be deleted. To avoid deleting these items, we first move them
-    // to the parent of the folder we're about to delete.
-    let needUpdate = new Set();
-    for (let syncId of this._foldersToDelete) {
-      let childSyncIds = yield PlacesSyncUtils.bookmarks.fetchChildSyncIds(syncId);
-      if (!childSyncIds.length) {
-        // No children -- just delete the folder.
-        yield this._deleteAtom(syncId)
-        continue;
-      }
-      // We could avoid some redundant work here by finding the nearest
-      // grandparent who isn't present in `this._toDelete`...
 
-      let grandparentSyncId = this.GUIDForId(
-        PlacesUtils.bookmarks.getFolderIdForItem(
-          this.idForGUID(PlacesSyncUtils.bookmarks.syncIdToGuid(syncId))));
+    // Two items are the same type if they have the same ItemType in Places,
+    // and also share some key characteristics (e.g., both being livemarks).
+    // We figure this out by examining the item to find the equivalent granular
+    // (string) type.
+    // If they're not the same type, we can't just update attributes. Delete
+    // then recreate the record instead.
+    let localItemType    = this._recordType(itemId);
+    let remoteRecordType = record.type;
+    this._log.trace("Local type: " + localItemType + ". " +
+                    "Remote type: " + remoteRecordType + ".");
+
+    if (localItemType != remoteRecordType) {
+      this._log.debug("Local record and remote record differ in type. " +
+                      "Deleting and recreating.");
+      this.removeById(itemId, record.id);
+      this.create(record);
+      return;
+    }
 
-      this._log.trace(`Moving ${childSyncIds.length} children of "${syncId}" to ` +
-                      `grandparent "${grandparentSyncId}" before deletion.`);
+    this._log.trace("Updating " + record.id + " (" + itemId + ")");
 
-      // Move children out of the parent and into the grandparent
-      yield Promise.all(childSyncIds.map(child => PlacesSyncUtils.bookmarks.update({
-        syncId: child,
-        parentSyncId: grandparentSyncId
-      })));
+    // Move the bookmark to a new parent or new position if necessary
+    if (record._parent > 0 &&
+        PlacesUtils.bookmarks.getFolderIdForItem(itemId) != record._parent) {
+      this._reparentItem(itemId, record._parent);
+    }
 
-      // Delete the (now empty) parent
-      try {
-        yield PlacesSyncUtils.bookmarks.remove(syncId, {
-          preventRemovalOfNonEmptyFolders: true
-        });
-      } catch (e) {
-        // We failed, probably because someone added something to this folder
-        // between when we got the children and now (or the database is corrupt,
-        // or something else happened...) This is unlikely, but possible. To
-        // avoid corruption in this case, we need to reupload the record to the
-        // server.
-        //
-        // (Ideally this whole operation would be done in a transaction, and this
-        // wouldn't be possible).
-        needUpdate.add(syncId);
+    for (let [key, val] in Iterator(record.cleartext)) {
+      switch (key) {
+      case "title":
+        PlacesUtils.bookmarks.setItemTitle(itemId, val);
+        break;
+      case "bmkUri":
+        PlacesUtils.bookmarks.changeBookmarkURI(itemId, Utils.makeURI(val));
+        break;
+      case "tags":
+        if (Array.isArray(val)) {
+          if (this.isTaggable(remoteRecordType)) {
+            this._tagID(itemId, val);
+          } else {
+            this._log.debug("Remote record type is invalid for tags: " + remoteRecordType);
+          }
+        }
+        break;
+      case "keyword":
+        PlacesUtils.bookmarks.setKeywordForBookmark(itemId, val);
+        break;
+      case "description":
+        if (val) {
+          PlacesUtils.annotations.setItemAnnotation(
+            itemId, DESCRIPTION_ANNO, val, 0,
+            PlacesUtils.annotations.EXPIRE_NEVER);
+        } else {
+          PlacesUtils.annotations.removeItemAnnotation(itemId, DESCRIPTION_ANNO);
+        }
+        break;
+      case "loadInSidebar":
+        if (val) {
+          PlacesUtils.annotations.setItemAnnotation(
+            itemId, SIDEBAR_ANNO, true, 0,
+            PlacesUtils.annotations.EXPIRE_NEVER);
+        } else {
+          PlacesUtils.annotations.removeItemAnnotation(itemId, SIDEBAR_ANNO);
+        }
+        break;
+      case "queryId":
+        PlacesUtils.annotations.setItemAnnotation(
+          itemId, SMART_BOOKMARKS_ANNO, val, 0,
+          PlacesUtils.annotations.EXPIRE_NEVER);
+        break;
       }
+    }
+  },
 
-      // Add children (for parentid) and grandparent (for children list) to set
-      // of records needing an update, *unless* they're marked for deletion.
-      if (!this._foldersToDelete.has(grandparentSyncId)) {
-        needUpdate.add(grandparentSyncId);
-      }
-      for (let childSyncId of childSyncIds) {
-        if (!this._foldersToDelete.has(childSyncId)) {
-          needUpdate.add(childSyncId);
+  _orderChildren: function _orderChildren() {
+    for (let [guid, children] in Iterator(this._childrenToOrder)) {
+      // Reorder children according to the GUID list. Gracefully deal
+      // with missing items, e.g. locally deleted.
+      let delta = 0;
+      let parent = null;
+      for (let idx = 0; idx < children.length; idx++) {
+        let itemid = this.idForGUID(children[idx]);
+        if (itemid == -1) {
+          delta += 1;
+          this._log.trace("Could not locate record " + children[idx]);
+          continue;
+        }
+        try {
+          // This code path could be optimized by caching the parent earlier.
+          // Doing so should take in count any edge case due to reparenting
+          // or parent invalidations though.
+          if (!parent) {
+            parent = PlacesUtils.bookmarks.getFolderIdForItem(itemid);
+          }
+          PlacesUtils.bookmarks.moveItem(itemid, parent, idx - delta);
+        } catch (ex) {
+          this._log.debug("Could not move item " + children[idx] + ": " + ex);
         }
       }
     }
-    return [...needUpdate];
-  }),
+  },
 
   changeItemID: function BStore_changeItemID(oldID, newID) {
     this._log.debug("Changing GUID " + oldID + " to " + newID);
 
-    Async.promiseSpinningly(PlacesSyncUtils.bookmarks.changeGuid(oldID, newID));
+    // Make sure there's an item to change GUIDs
+    let itemId = this.idForGUID(oldID);
+    if (itemId <= 0)
+      return;
+
+    this._setGUID(itemId, newID);
+  },
+
+  _getNode: function BStore__getNode(folder) {
+    let query = PlacesUtils.history.getNewQuery();
+    query.setFolders([folder], 1);
+    return PlacesUtils.history.executeQuery(
+      query, PlacesUtils.history.getNewQueryOptions()).root;
+  },
+
+  _getTags: function BStore__getTags(uri) {
+    try {
+      if (typeof(uri) == "string")
+        uri = Utils.makeURI(uri);
+    } catch(e) {
+      this._log.warn("Could not parse URI \"" + uri + "\": " + e);
+    }
+    return PlacesUtils.tagging.getTagsForURI(uri, {});
+  },
+
+  _getDescription: function BStore__getDescription(id) {
+    try {
+      return PlacesUtils.annotations.getItemAnnotation(id, DESCRIPTION_ANNO);
+    } catch (e) {
+      return null;
+    }
+  },
+
+  _isLoadInSidebar: function BStore__isLoadInSidebar(id) {
+    return PlacesUtils.annotations.itemHasAnnotation(id, SIDEBAR_ANNO);
+  },
+
+  get _childGUIDsStm() {
+    return this._getStmt(
+      "SELECT id AS item_id, guid " +
+      "FROM moz_bookmarks " +
+      "WHERE parent = :parent " +
+      "ORDER BY position");
+  },
+  _childGUIDsCols: ["item_id", "guid"],
+
+  _getChildGUIDsForId: function _getChildGUIDsForId(itemid) {
+    let stmt = this._childGUIDsStm;
+    stmt.params.parent = itemid;
+    let rows = Async.querySpinningly(stmt, this._childGUIDsCols);
+    return rows.map(function (row) {
+      if (row.guid) {
+        return row.guid;
+      }
+      // A GUID hasn't been assigned to this item yet, do this now.
+      return this.GUIDForId(row.item_id);
+    }, this);
   },
 
   // Create a record starting from the weave id (places guid)
   createRecord: function createRecord(id, collection) {
-    let item = Async.promiseSpinningly(PlacesSyncUtils.bookmarks.fetch(id));
-    if (!item) { // deleted item
-      let record = new PlacesItem(collection, id);
+    let placeId = this.idForGUID(id);
+    let record;
+    if (placeId <= 0) { // deleted item
+      record = new PlacesItem(collection, id);
       record.deleted = true;
       return record;
     }
 
-    let recordObj = getTypeObject(item.kind);
-    if (!recordObj) {
-      this._log.warn("Unknown item type, cannot serialize: " + item.kind);
-      recordObj = PlacesItem;
+    let parent = PlacesUtils.bookmarks.getFolderIdForItem(placeId);
+    switch (PlacesUtils.bookmarks.getItemType(placeId)) {
+    case PlacesUtils.bookmarks.TYPE_BOOKMARK:
+      let bmkUri = PlacesUtils.bookmarks.getBookmarkURI(placeId).spec;
+      if (bmkUri.indexOf("place:") == 0) {
+        record = new BookmarkQuery(collection, id);
+
+        // Get the actual tag name instead of the local itemId
+        let folder = bmkUri.match(/[:&]folder=(\d+)/);
+        try {
+          // There might not be the tag yet when creating on a new client
+          if (folder != null) {
+            folder = folder[1];
+            record.folderName = PlacesUtils.bookmarks.getItemTitle(folder);
+            this._log.trace("query id: " + folder + " = " + record.folderName);
+          }
+        }
+        catch(ex) {}
+        
+        // Persist the Smart Bookmark anno, if found.
+        try {
+          let anno = PlacesUtils.annotations.getItemAnnotation(placeId, SMART_BOOKMARKS_ANNO);
+          if (anno != null) {
+            this._log.trace("query anno: " + SMART_BOOKMARKS_ANNO +
+                            " = " + anno);
+            record.queryId = anno;
+          }
+        }
+        catch(ex) {}
+      }
+      else {
+        record = new Bookmark(collection, id);
+      }
+      record.title = PlacesUtils.bookmarks.getItemTitle(placeId);
+
+      record.parentName = PlacesUtils.bookmarks.getItemTitle(parent);
+      record.bmkUri = bmkUri;
+      record.tags = this._getTags(record.bmkUri);
+      record.keyword = PlacesUtils.bookmarks.getKeywordForBookmark(placeId);
+      record.description = this._getDescription(placeId);
+      record.loadInSidebar = this._isLoadInSidebar(placeId);
+      break;
+
+    case PlacesUtils.bookmarks.TYPE_FOLDER:
+      if (PlacesUtils.annotations
+                     .itemHasAnnotation(placeId, PlacesUtils.LMANNO_FEEDURI)) {
+        record = new Livemark(collection, id);
+        let as = PlacesUtils.annotations;
+        record.feedUri = as.getItemAnnotation(placeId, PlacesUtils.LMANNO_FEEDURI);
+        try {
+          record.siteUri = as.getItemAnnotation(placeId, PlacesUtils.LMANNO_SITEURI);
+        } catch (ex) {}
+      } else {
+        record = new BookmarkFolder(collection, id);
+      }
+
+      if (parent > 0)
+        record.parentName = PlacesUtils.bookmarks.getItemTitle(parent);
+      record.title = PlacesUtils.bookmarks.getItemTitle(placeId);
+      record.description = this._getDescription(placeId);
+      record.children = this._getChildGUIDsForId(placeId);
+      break;
+
+    case PlacesUtils.bookmarks.TYPE_SEPARATOR:
+      record = new BookmarkSeparator(collection, id);
+      if (parent > 0)
+        record.parentName = PlacesUtils.bookmarks.getItemTitle(parent);
+      // Create a positioning identifier for the separator, used by _mapDupe
+      record.pos = PlacesUtils.bookmarks.getItemIndex(placeId);
+      break;
+
+    default:
+      record = new PlacesItem(collection, id);
+      this._log.warn("Unknown item type, cannot serialize: " +
+                     PlacesUtils.bookmarks.getItemType(placeId));
     }
-    let record = new recordObj(collection, id);
-    record.fromSyncBookmark(item);
 
+    record.parentid = this.GUIDForId(parent);
     record.sortindex = this._calculateIndex(record);
 
     return record;
@@ -997,22 +1118,84 @@ BookmarksStore.prototype = {
     return this._getStmt(
         "SELECT frecency " +
         "FROM moz_places " +
-        "WHERE url_hash = hash(:url) AND url = :url " +
+        "WHERE url = :url " +
         "LIMIT 1");
   },
   _frecencyCols: ["frecency"],
 
+  get _setGUIDStm() {
+    return this._getStmt(
+      "UPDATE moz_bookmarks " +
+      "SET guid = :guid " +
+      "WHERE id = :item_id");
+  },
+
+  // Some helper functions to handle GUIDs
+  _setGUID: function _setGUID(id, guid) {
+    if (!guid)
+      guid = Utils.makeGUID();
+
+    let stmt = this._setGUIDStm;
+    stmt.params.guid = guid;
+    stmt.params.item_id = id;
+    Async.querySpinningly(stmt);
+    return guid;
+  },
+
+  get _guidForIdStm() {
+    return this._getStmt(
+      "SELECT guid " +
+      "FROM moz_bookmarks " +
+      "WHERE id = :item_id");
+  },
+  _guidForIdCols: ["guid"],
+
   GUIDForId: function GUIDForId(id) {
-    let guid = Async.promiseSpinningly(PlacesUtils.promiseItemGuid(id));
-    return PlacesSyncUtils.bookmarks.guidToSyncId(guid);
+    let special = kSpecialIds.specialGUIDForId(id);
+    if (special)
+      return special;
+
+    let stmt = this._guidForIdStm;
+    stmt.params.item_id = id;
+
+    // Use the existing GUID if it exists
+    let result = Async.querySpinningly(stmt, this._guidForIdCols)[0];
+    if (result && result.guid)
+      return result.guid;
+
+    // Give the uri a GUID if it doesn't have one
+    return this._setGUID(id);
   },
 
-  idForGUID: function idForGUID(guid) {
-    // guid might be a String object rather than a string.
-    guid = PlacesSyncUtils.bookmarks.syncIdToGuid(guid.toString());
+  get _idForGUIDStm() {
+    return this._getStmt(
+      "SELECT id AS item_id " +
+      "FROM moz_bookmarks " +
+      "WHERE guid = :guid");
+  },
+  _idForGUIDCols: ["item_id"],
+
+  // noCreate is provided as an optional argument to prevent the creation of
+  // non-existent special records, such as "mobile".
+  idForGUID: function idForGUID(guid, noCreate) {
+    if (kSpecialIds.isSpecialGUID(guid))
+      return kSpecialIds.specialIdForGUID(guid, !noCreate);
 
-    return Async.promiseSpinningly(PlacesUtils.promiseItemId(guid).catch(
-      ex => -1));
+    let stmt = this._idForGUIDStm;
+    // guid might be a String object rather than a string.
+    stmt.params.guid = guid.toString();
+
+    let results = Async.querySpinningly(stmt, this._idForGUIDCols);
+    this._log.trace("Number of rows matching GUID " + guid + ": "
+                    + results.length);
+    
+    // Here's the one we care about: the first.
+    let result = results[0];
+    
+    if (!result)
+      return -1;
+    
+    return result.item_id;
   },
 
   _calculateIndex: function _calculateIndex(record) {
@@ -1037,48 +1220,107 @@ BookmarksStore.prototype = {
     return index;
   },
 
-  getAllIDs: function BStore_getAllIDs() {
-    let items = {};
-
-    let query = `
-      WITH RECURSIVE
-      changeRootContents(id) AS (
-        VALUES ${getChangeRootIds().map(id => `(${id})`).join(", ")}
-        UNION ALL
-        SELECT b.id
-        FROM moz_bookmarks b
-        JOIN changeRootContents c ON b.parent = c.id
-      )
-      SELECT guid
-      FROM changeRootContents
-      JOIN moz_bookmarks USING (id)
-    `;
-
-    let statement = this._getStmt(query);
-    let results = Async.querySpinningly(statement, ["guid"]);
-    for (let { guid } of results) {
-      let syncID = PlacesSyncUtils.bookmarks.guidToSyncId(guid);
-      items[syncID] = { modified: 0, deleted: false };
+  _getChildren: function BStore_getChildren(guid, items) {
+    let node = guid; // the recursion case
+    if (typeof(node) == "string") { // callers will give us the guid as the first arg
+      let nodeID = this.idForGUID(guid, true);
+      if (!nodeID) {
+        this._log.debug("No node for GUID " + guid + "; returning no children.");
+        return items;
+      }
+      node = this._getNode(nodeID);
+    }
+    
+    if (node.type == node.RESULT_TYPE_FOLDER) {
+      node.QueryInterface(Ci.nsINavHistoryQueryResultNode);
+      node.containerOpen = true;
+      try {
+        // Remember all the children GUIDs and recursively get more
+        for (let i = 0; i < node.childCount; i++) {
+          let child = node.getChild(i);
+          items[this.GUIDForId(child.itemId)] = true;
+          this._getChildren(child, items);
+        }
+      }
+      finally {
+        node.containerOpen = false;
+      }
     }
 
     return items;
   },
 
+  /**
+   * Associates the URI of the item with the provided ID with the
+   * provided array of tags.
+   * If the provided ID does not identify an item with a URI,
+   * returns immediately.
+   */
+  _tagID: function _tagID(itemID, tags) {
+    if (!itemID || !tags) {
+      return;
+    }
+
+    try {
+      let u = PlacesUtils.bookmarks.getBookmarkURI(itemID);
+      this._tagURI(u, tags);
+    } catch (e) {
+      this._log.warn("Got exception fetching URI for " + itemID + ": not tagging. " +
+                     Utils.exceptionStr(e));
+
+      // I guess it doesn't have a URI. Don't try to tag it.
+      return;
+    }
+  },
+
+  /**
+   * Associate the provided URI with the provided array of tags.
+   * If the provided URI is falsy, returns immediately.
+   */
+  _tagURI: function _tagURI(bookmarkURI, tags) {
+    if (!bookmarkURI || !tags) {
+      return;
+    }
+
+    // Filter out any null/undefined/empty tags.
+    tags = tags.filter(t => t);
+
+    // Temporarily tag a dummy URI to preserve tag ids when untagging.
+    let dummyURI = Utils.makeURI("about:weave#BStore_tagURI");
+    PlacesUtils.tagging.tagURI(dummyURI, tags);
+    PlacesUtils.tagging.untagURI(bookmarkURI, null);
+    PlacesUtils.tagging.tagURI(bookmarkURI, tags);
+    PlacesUtils.tagging.untagURI(dummyURI, null);
+  },
+
+  getAllIDs: function BStore_getAllIDs() {
+    let items = {"menu": true,
+                 "toolbar": true};
+    for each (let guid in kSpecialIds.guids) {
+      if (guid != "places" && guid != "tags")
+        this._getChildren(guid, items);
+    }
+    return items;
+  },
+
   wipe: function BStore_wipe() {
-    this.clearPendingDeletions();
-    Async.promiseSpinningly(Task.spawn(function* () {
+    let cb = Async.makeSpinningCallback();
+    Task.spawn(function() {
       // Save a backup before clearing out all bookmarks.
       yield PlacesBackups.create(null, true);
-      yield PlacesUtils.bookmarks.eraseEverything({
-        source: SOURCE_SYNC,
-      });
-    }));
+      for each (let guid in kSpecialIds.guids)
+        if (guid != "places") {
+          let id = kSpecialIds.specialIdForGUID(guid);
+          if (id)
+            PlacesUtils.bookmarks.removeFolderChildren(id);
+        }
+      cb();
+    });
+    cb.wait();
   }
 };
 
 function BookmarksTracker(name, engine) {
-  this._batchDepth = 0;
-  this._batchSawScoreIncrement = false;
   Tracker.call(this, name, engine);
 
   Svc.Obs.add("places-shutdown", this);
@@ -1086,16 +1328,6 @@ function BookmarksTracker(name, engine) {
 BookmarksTracker.prototype = {
   __proto__: Tracker.prototype,
 
-  //`_ignore` checks the change source for each observer notification, so we
-  // don't want to let the engine ignore all changes during a sync.
-  get ignoreAll() {
-    return false;
-  },
-
-  // Define an empty setter so that the engine doesn't throw a `TypeError`
-  // setting a read-only property.
-  set ignoreAll(value) {},
-
   startTracking: function() {
     PlacesUtils.bookmarks.addObserver(this, true);
     Svc.Obs.add("bookmarks-restore-begin", this);
@@ -1116,9 +1348,11 @@ BookmarksTracker.prototype = {
     switch (topic) {
       case "bookmarks-restore-begin":
         this._log.debug("Ignoring changes from importing bookmarks.");
+        this.ignoreAll = true;
         break;
       case "bookmarks-restore-success":
         this._log.debug("Tracking all items on successful import.");
+        this.ignoreAll = false;
 
         this._log.debug("Restore succeeded: wiping server and other clients.");
         this.engine.service.resetClient([this.name]);
@@ -1127,6 +1361,7 @@ BookmarksTracker.prototype = {
         break;
       case "bookmarks-restore-failed":
         this._log.debug("Tracking all items on failed import.");
+        this.ignoreAll = false;
         break;
     }
   },
@@ -1137,68 +1372,73 @@ BookmarksTracker.prototype = {
     Ci.nsISupportsWeakReference
   ]),
 
-  addChangedID(id, change) {
-    if (!id) {
-      this._log.warn("Attempted to add undefined ID to tracker");
-      return false;
-    }
-    if (this._ignored.includes(id)) {
-      return false;
-    }
-    let shouldSaveChange = false;
-    let currentChange = this.changedIDs[id];
-    if (currentChange) {
-      if (typeof currentChange == "number") {
-        // Allow raw timestamps for backward-compatibility with persisted
-        // changed IDs. The new format uses tuples to track deleted items.
-        shouldSaveChange = currentChange < change.modified;
-      } else {
-        shouldSaveChange = currentChange.modified < change.modified ||
-                           currentChange.deleted != change.deleted;
-      }
-    } else {
-      shouldSaveChange = true;
-    }
-    if (shouldSaveChange) {
-      this._saveChangedID(id, change);
-    }
-    return true;
-  },
-
   /**
    * Add a bookmark GUID to be uploaded and bump up the sync score.
    *
-   * @param itemId
-   *        The Places item ID of the bookmark to upload.
-   * @param guid
-   *        The Places GUID of the bookmark to upload.
-   * @param isTombstone
-   *        Whether we're uploading a tombstone for a removed bookmark.
+   * @param itemGuid
+   *        GUID of the bookmark to upload.
    */
-  _add: function BMT__add(itemId, guid, isTombstone = false) {
-    let syncID = PlacesSyncUtils.bookmarks.guidToSyncId(guid);
-    let info = { modified: Date.now() / 1000, deleted: isTombstone };
-    if (this.addChangedID(syncID, info)) {
+  _add: function BMT__add(itemId, guid) {
+    guid = kSpecialIds.specialGUIDForId(itemId) || guid;
+    if (this.addChangedID(guid))
       this._upScore();
-    }
   },
 
-  /* Every add/remove/change will trigger a sync for MULTI_DEVICE (except in
-     a batch operation, where we do it at the end of the batch) */
+  /* Every add/remove/change will trigger a sync for MULTI_DEVICE. */
   _upScore: function BMT__upScore() {
-    if (this._batchDepth == 0) {
-      this.score += SCORE_INCREMENT_XLARGE;
-    } else {
-      this._batchSawScoreIncrement = true;
+    this.score += SCORE_INCREMENT_XLARGE;
+  },
+
+  /**
+   * Determine if a change should be ignored.
+   *
+   * @param itemId
+   *        Item under consideration to ignore
+   * @param folder (optional)
+   *        Folder of the item being changed
+   */
+  _ignore: function BMT__ignore(itemId, folder, guid) {
+    // Ignore unconditionally if the engine tells us to.
+    if (this.ignoreAll)
+      return true;
+
+    // Get the folder id if we weren't given one.
+    if (folder == null) {
+      try {
+        folder = PlacesUtils.bookmarks.getFolderIdForItem(itemId);
+      } catch (ex) {
+        this._log.debug("getFolderIdForItem(" + itemId +
+                        ") threw; calling _ensureMobileQuery.");
+        // I'm guessing that gFIFI can throw, and perhaps that's why
+        // _ensureMobileQuery is here at all. Try not to call it.
+        this._ensureMobileQuery();
+        folder = PlacesUtils.bookmarks.getFolderIdForItem(itemId);
+      }
+    }
+
+    // Ignore changes to tags (folders under the tags folder).
+    let tags = kSpecialIds.tags;
+    if (folder == tags)
+      return true;
+
+    // Ignore tag items (the actual instance of a tag for a bookmark).
+    if (PlacesUtils.bookmarks.getFolderIdForItem(folder) == tags)
+      return true;
+
+    // Make sure to remove items that have the exclude annotation.
+    if (PlacesUtils.annotations.itemHasAnnotation(itemId, EXCLUDEBACKUP_ANNO)) {
+      this.removeChangedID(guid);
+      return true;
     }
+
+    return false;
   },
 
   onItemAdded: function BMT_onItemAdded(itemId, folder, index,
                                         itemType, uri, title, dateAdded,
-                                        guid, parentGuid, source) {
-    if (IGNORED_SOURCES.includes(source)) {
+                                        guid, parentGuid) {
+    if (this._ignore(itemId, folder, guid))
       return;
-    }
 
     this._log.trace("onItemAdded: " + itemId);
     this._add(itemId, guid);
@@ -1206,51 +1446,13 @@ BookmarksTracker.prototype = {
   },
 
   onItemRemoved: function (itemId, parentId, index, type, uri,
-                           guid, parentGuid, source) {
-    if (IGNORED_SOURCES.includes(source)) {
-      return;
-    }
-
-    // Ignore changes to tags (folders under the tags folder).
-    if (parentId == PlacesUtils.tagsFolderId) {
-      return;
-    }
-
-    let grandParentId = -1;
-    try {
-      grandParentId = PlacesUtils.bookmarks.getFolderIdForItem(parentId);
-    } catch (ex) {
-      // `getFolderIdForItem` can throw if the item no longer exists, such as
-      // when we've removed a subtree using `removeFolderChildren`.
-      return;
-    }
-
-    // Ignore tag items (the actual instance of a tag for a bookmark).
-    if (grandParentId == PlacesUtils.tagsFolderId) {
+                           guid, parentGuid) {
+    if (this._ignore(itemId, parentId, guid)) {
       return;
     }
 
-    /**
-     * The above checks are incomplete: we can still write tombstones for
-     * items that we don't track, and upload extraneous roots.
-     *
-     * Consider the left pane root: it's a child of the Places root, and has
-     * children and grandchildren. `PlacesUIUtils` can create, delete, and
-     * recreate it as needed. We can't determine ancestors when the root or its
-     * children are deleted, because they've already been removed from the
-     * database when `onItemRemoved` is called. Likewise, we can't check their
-     * "exclude from backup" annos, because they've *also* been removed.
-     *
-     * So, we end up writing tombstones for the left pane queries and left
-     * pane root. For good measure, we'll also upload the Places root, because
-     * it's the parent of the left pane root.
-     *
-     * As a workaround, we can track the parent GUID and reconstruct the item's
-     * ancestry at sync time. This is complicated, and the previous behavior was
-     * already wrong, so we'll wait for bug 1258127 to fix this generally.
-     */
     this._log.trace("onItemRemoved: " + itemId);
-    this._add(itemId, guid, /* isTombstone */ true);
+    this._add(itemId, guid);
     this._add(parentId, parentGuid);
   },
 
@@ -1265,40 +1467,32 @@ BookmarksTracker.prototype = {
     if (all.length == 0)
       return;
 
+    // Disable handling of notifications while changing the mobile query
+    this.ignoreAll = true;
+
     let mobile = find(MOBILE_ANNO);
-    let queryURI = Utils.makeURI("place:folder=" + PlacesUtils.mobileFolderId);
-    let title = PlacesBundle.GetStringFromName("MobileBookmarksFolderTitle");
+    let queryURI = Utils.makeURI("place:folder=" + kSpecialIds.mobile);
+    let title = Str.sync.get("mobile.label");
 
     // Don't add OR remove the mobile bookmarks if there's nothing.
-    if (PlacesUtils.bookmarks.getIdForItemAt(PlacesUtils.mobileFolderId, 0) == -1) {
+    if (PlacesUtils.bookmarks.getIdForItemAt(kSpecialIds.mobile, 0) == -1) {
       if (mobile.length != 0)
-        PlacesUtils.bookmarks.removeItem(mobile[0], SOURCE_SYNC);
+        PlacesUtils.bookmarks.removeItem(mobile[0]);
     }
     // Add the mobile bookmarks query if it doesn't exist
     else if (mobile.length == 0) {
-      let query = PlacesUtils.bookmarks.insertBookmark(all[0], queryURI, -1, title, /* guid */ null, SOURCE_SYNC);
+      let query = PlacesUtils.bookmarks.insertBookmark(all[0], queryURI, -1, title);
       PlacesUtils.annotations.setItemAnnotation(query, ORGANIZERQUERY_ANNO, MOBILE_ANNO, 0,
-                                  PlacesUtils.annotations.EXPIRE_NEVER, SOURCE_SYNC);
-      PlacesUtils.annotations.setItemAnnotation(query, PlacesUtils.EXCLUDE_FROM_BACKUP_ANNO, 1, 0,
-                                  PlacesUtils.annotations.EXPIRE_NEVER, SOURCE_SYNC);
+                                  PlacesUtils.annotations.EXPIRE_NEVER);
+      PlacesUtils.annotations.setItemAnnotation(query, EXCLUDEBACKUP_ANNO, 1, 0,
+                                  PlacesUtils.annotations.EXPIRE_NEVER);
     }
-    // Make sure the existing query URL and title are correct
-    else {
-      if (!PlacesUtils.bookmarks.getBookmarkURI(mobile[0]).equals(queryURI)) {
-        PlacesUtils.bookmarks.changeBookmarkURI(mobile[0], queryURI,
-                                                SOURCE_SYNC);
-      }
-      let queryTitle = PlacesUtils.bookmarks.getItemTitle(mobile[0]);
-      if (queryTitle != title) {
-        PlacesUtils.bookmarks.setItemTitle(mobile[0], title, SOURCE_SYNC);
-      }
-      let rootTitle =
-        PlacesUtils.bookmarks.getItemTitle(PlacesUtils.mobileFolderId);
-      if (rootTitle != title) {
-        PlacesUtils.bookmarks.setItemTitle(PlacesUtils.mobileFolderId, title,
-                                           SOURCE_SYNC);
-      }
+    // Make sure the existing title is correct
+    else if (PlacesUtils.bookmarks.getItemTitle(mobile[0]) != title) {
+      PlacesUtils.bookmarks.setItemTitle(mobile[0], title);
     }
+
+    this.ignoreAll = false;
   },
 
   // This method is oddly structured, but the idea is to return as quickly as
@@ -1306,11 +1500,10 @@ BookmarksTracker.prototype = {
   // *each change*.
   onItemChanged: function BMT_onItemChanged(itemId, property, isAnno, value,
                                             lastModified, itemType, parentId,
-                                            guid, parentGuid, oldValue,
-                                            source) {
-    if (IGNORED_SOURCES.includes(source)) {
+                                            guid, parentGuid) {
+    // Quicker checks first.
+    if (this.ignoreAll)
       return;
-    }
 
     if (isAnno && (ANNOS_TO_TRACK.indexOf(property) == -1))
       // Ignore annotations except for the ones that we sync.
@@ -1320,6 +1513,9 @@ BookmarksTracker.prototype = {
     if (property == "favicon")
       return;
 
+    if (this._ignore(itemId, parentId, guid))
+      return;
+
     this._log.trace("onItemChanged: " + itemId +
                     (", " + property + (isAnno? " (anno)" : "")) +
                     (value ? (" = \"" + value + "\"") : ""));
@@ -1328,11 +1524,9 @@ BookmarksTracker.prototype = {
 
   onItemMoved: function BMT_onItemMoved(itemId, oldParent, oldIndex,
                                         newParent, newIndex, itemType,
-                                        guid, oldParentGuid, newParentGuid,
-                                        source) {
-    if (IGNORED_SOURCES.includes(source)) {
+                                        guid, oldParentGuid, newParentGuid) {
+    if (this._ignore(itemId, newParent, guid))
       return;
-    }
 
     this._log.trace("onItemMoved: " + itemId);
     this._add(oldParent, oldParentGuid);
@@ -1342,37 +1536,10 @@ BookmarksTracker.prototype = {
     }
 
     // Remove any position annotations now that the user moved the item
-    PlacesUtils.annotations.removeItemAnnotation(itemId,
-      PlacesSyncUtils.bookmarks.SYNC_PARENT_ANNO, SOURCE_SYNC);
+    PlacesUtils.annotations.removeItemAnnotation(itemId, PARENT_ANNO);
   },
 
-  onBeginUpdateBatch: function () {
-    ++this._batchDepth;
-  },
-  onEndUpdateBatch: function () {
-    if (--this._batchDepth === 0 && this._batchSawScoreIncrement) {
-      this.score += SCORE_INCREMENT_XLARGE;
-      this._batchSawScoreIncrement = false;
-    }
-  },
+  onBeginUpdateBatch: function () {},
+  onEndUpdateBatch: function () {},
   onItemVisited: function () {}
 };
-
-// Returns an array of root IDs to recursively query for synced bookmarks.
-// Items in other roots, including tags and organizer queries, will be
-// ignored.
-function getChangeRootIds() {
-  return [
-    PlacesUtils.bookmarksMenuFolderId,
-    PlacesUtils.toolbarFolderId,
-    PlacesUtils.unfiledBookmarksFolderId,
-    PlacesUtils.mobileFolderId,
-  ];
-}
-
-class BookmarksChangeset extends Changeset {
-  getModifiedTimestamp(id) {
-    let change = this.changes[id];
-    return change ? change.modified : Number.NaN;
-  }
-}
diff --git a/services/sync/modules/engines/clients.js b/services/sync/modules/engines/clients.js
index 3dd679570..f423242c9 100644
--- a/services/sync/modules/engines/clients.js
+++ b/services/sync/modules/engines/clients.js
@@ -2,57 +2,24 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-/**
- * How does the clients engine work?
- *
- * - We use 2 files - commands.json and commands-syncing.json.
- *
- * - At sync upload time, we attempt a rename of commands.json to
- *   commands-syncing.json, and ignore errors (helps for crash during sync!).
- * - We load commands-syncing.json and stash the contents in
- *   _currentlySyncingCommands which lives for the duration of the upload process.
- * - We use _currentlySyncingCommands to build the outgoing records
- * - Immediately after successful upload, we delete commands-syncing.json from
- *   disk (and clear _currentlySyncingCommands). We reconcile our local records
- *   with what we just wrote in the server, and add failed IDs commands
- *   back in commands.json
- * - Any time we need to "save" a command for future syncs, we load
- *   commands.json, update it, and write it back out.
- */
-
 this.EXPORTED_SYMBOLS = [
   "ClientEngine",
   "ClientsRec"
 ];
 
-var {classes: Cc, interfaces: Ci, utils: Cu} = Components;
+const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
 
-Cu.import("resource://services-common/async.js");
 Cu.import("resource://services-common/stringbundle.js");
 Cu.import("resource://services-sync/constants.js");
 Cu.import("resource://services-sync/engines.js");
 Cu.import("resource://services-sync/record.js");
-Cu.import("resource://services-sync/resource.js");
 Cu.import("resource://services-sync/util.js");
-Cu.import("resource://gre/modules/Services.jsm");
-
-XPCOMUtils.defineLazyModuleGetter(this, "fxAccounts",
-  "resource://gre/modules/FxAccounts.jsm");
 
 const CLIENTS_TTL = 1814400; // 21 days
 const CLIENTS_TTL_REFRESH = 604800; // 7 days
-const STALE_CLIENT_REMOTE_AGE = 604800; // 7 days
 
 const SUPPORTED_PROTOCOL_VERSIONS = ["1.1", "1.5"];
 
-function hasDupeCommand(commands, action) {
-  if (!commands) {
-    return false;
-  }
-  return commands.some(other => other.command == action.command &&
-    Utils.deepEquals(other.args, action.args));
-}
-
 this.ClientsRec = function ClientsRec(collection, id) {
   CryptoWrapper.call(this, collection, id);
 }
@@ -66,27 +33,23 @@ Utils.deferGetSet(ClientsRec,
                   "cleartext",
                   ["name", "type", "commands",
                    "version", "protocols",
-                   "formfactor", "os", "appPackage", "application", "device",
-                   "fxaDeviceId"]);
+                   "formfactor", "os", "appPackage", "application", "device"]);
 
 
 this.ClientEngine = function ClientEngine(service) {
   SyncEngine.call(this, "Clients", service);
 
-  // Reset the last sync timestamp on every startup so that we fetch all clients
-  this.resetLastSync();
+  // Reset the client on every startup so that we fetch recent clients
+  this._resetClient();
 }
 ClientEngine.prototype = {
   __proto__: SyncEngine.prototype,
   _storeObj: ClientStore,
   _recordObj: ClientsRec,
   _trackerObj: ClientsTracker,
-  allowSkippedRecord: false,
 
   // Always sync client data as it controls other sync behavior
-  get enabled() {
-    return true;
-  },
+  get enabled() true,
 
   get lastRecordUpload() {
     return Svc.Prefs.get(this.name + ".lastRecordUpload", 0);
@@ -95,31 +58,18 @@ ClientEngine.prototype = {
     Svc.Prefs.set(this.name + ".lastRecordUpload", Math.floor(value));
   },
 
-  get remoteClients() {
-    // return all non-stale clients for external consumption.
-    return Object.values(this._store._remoteClients).filter(v => !v.stale);
-  },
-
-  remoteClientExists(id) {
-    let client = this._store._remoteClients[id];
-    return !!(client && !client.stale);
-  },
-
   // Aggregate some stats on the composition of clients on this account
   get stats() {
     let stats = {
-      hasMobile: this.localType == DEVICE_TYPE_MOBILE,
+      hasMobile: this.localType == "mobile",
       names: [this.localName],
       numClients: 1,
     };
 
-    for (let id in this._store._remoteClients) {
-      let {name, type, stale} = this._store._remoteClients[id];
-      if (!stale) {
-        stats.hasMobile = stats.hasMobile || type == DEVICE_TYPE_MOBILE;
-        stats.names.push(name);
-        stats.numClients++;
-      }
+    for each (let {name, type} in this._store._remoteClients) {
+      stats.hasMobile = stats.hasMobile || type == "mobile";
+      stats.names.push(name);
+      stats.numClients++;
     }
 
     return stats;
@@ -135,11 +85,7 @@ ClientEngine.prototype = {
 
     counts.set(this.localType, 1);
 
-    for (let id in this._store._remoteClients) {
-      let record = this._store._remoteClients[id];
-      if (record.stale) {
-        continue; // pretend "stale" records don't exist.
-      }
+    for each (let record in this._store._remoteClients) {
       let type = record.type;
       if (!counts.has(type)) {
         counts.set(type, 0);
@@ -156,9 +102,7 @@ ClientEngine.prototype = {
     let localID = Svc.Prefs.get("client.GUID", "");
     return localID == "" ? this.localID = Utils.makeGUID() : localID;
   },
-  set localID(value) {
-    Svc.Prefs.set("client.GUID", value);
-  },
+  set localID(value) Svc.Prefs.set("client.GUID", value),
 
   get brandName() {
     let brand = new StringBundle("chrome://branding/locale/brand.properties");
@@ -166,97 +110,23 @@ ClientEngine.prototype = {
   },
 
   get localName() {
-    let name = Utils.getDeviceName();
-    // If `getDeviceName` returns the default name, set the pref. FxA registers
-    // the device before syncing, so we don't need to update the registration
-    // in this case.
-    Svc.Prefs.set("client.name", name);
-    return name;
-  },
-  set localName(value) {
-    Svc.Prefs.set("client.name", value);
-    // Update the registration in the background.
-    fxAccounts.updateDeviceRegistration().catch(error => {
-      this._log.warn("failed to update fxa device registration", error);
-    });
-  },
+    let localName = Svc.Prefs.get("client.name", "");
+    if (localName != "")
+      return localName;
 
-  get localType() {
-    return Utils.getDeviceType();
-  },
-  set localType(value) {
-    Svc.Prefs.set("client.type", value);
+    return this.localName = Utils.getDefaultDeviceName();
   },
+  set localName(value) Svc.Prefs.set("client.name", value),
 
-  getClientName(id) {
-    if (id == this.localID) {
-      return this.localName;
-    }
-    let client = this._store._remoteClients[id];
-    return client ? client.name : "";
-  },
-
-  getClientFxaDeviceId(id) {
-    if (this._store._remoteClients[id]) {
-      return this._store._remoteClients[id].fxaDeviceId;
-    }
-    return null;
-  },
+  get localType() Svc.Prefs.get("client.type", "desktop"),
+  set localType(value) Svc.Prefs.set("client.type", value),
 
   isMobile: function isMobile(id) {
     if (this._store._remoteClients[id])
-      return this._store._remoteClients[id].type == DEVICE_TYPE_MOBILE;
+      return this._store._remoteClients[id].type == "mobile";
     return false;
   },
 
-  _readCommands() {
-    let cb = Async.makeSpinningCallback();
-    Utils.jsonLoad("commands", this, commands => cb(null, commands));
-    return cb.wait() || {};
-  },
-
-  /**
-   * Low level function, do not use directly (use _addClientCommand instead).
-   */
-  _saveCommands(commands) {
-    let cb = Async.makeSpinningCallback();
-    Utils.jsonSave("commands", this, commands, error => {
-      if (error) {
-        this._log.error("Failed to save JSON outgoing commands", error);
-      }
-      cb();
-    });
-    cb.wait();
-  },
-
-  _prepareCommandsForUpload() {
-    let cb = Async.makeSpinningCallback();
-    Utils.jsonMove("commands", "commands-syncing", this).catch(() => {}) // Ignore errors
-      .then(() => {
-        Utils.jsonLoad("commands-syncing", this, commands => cb(null, commands));
-      });
-    return cb.wait() || {};
-  },
-
-  _deleteUploadedCommands() {
-    delete this._currentlySyncingCommands;
-    Async.promiseSpinningly(
-      Utils.jsonRemove("commands-syncing", this).catch(err => {
-        this._log.error("Failed to delete syncing-commands file", err);
-      })
-    );
-  },
-
-  _addClientCommand(clientId, command) {
-    const allCommands = this._readCommands();
-    const clientCommands = allCommands[clientId] || [];
-    if (hasDupeCommand(clientCommands, command)) {
-      return;
-    }
-    allCommands[clientId] = clientCommands.concat(command);
-    this._saveCommands(allCommands);
-  },
-
   _syncStartup: function _syncStartup() {
     // Reupload new client record periodically.
     if (Date.now() / 1000 - this.lastRecordUpload > CLIENTS_TTL_REFRESH) {
@@ -266,157 +136,9 @@ ClientEngine.prototype = {
     SyncEngine.prototype._syncStartup.call(this);
   },
 
-  _processIncoming() {
-    // Fetch all records from the server.
-    this.lastSync = 0;
-    this._incomingClients = {};
-    try {
-      SyncEngine.prototype._processIncoming.call(this);
-      // Since clients are synced unconditionally, any records in the local store
-      // that don't exist on the server must be for disconnected clients. Remove
-      // them, so that we don't upload records with commands for clients that will
-      // never see them. We also do this to filter out stale clients from the
-      // tabs collection, since showing their list of tabs is confusing.
-      for (let id in this._store._remoteClients) {
-        if (!this._incomingClients[id]) {
-          this._log.info(`Removing local state for deleted client ${id}`);
-          this._removeRemoteClient(id);
-        }
-      }
-      // Bug 1264498: Mobile clients don't remove themselves from the clients
-      // collection when the user disconnects Sync, so we mark as stale clients
-      // with the same name that haven't synced in over a week.
-      // (Note we can't simply delete them, or we re-apply them next sync - see
-      // bug 1287687)
-      delete this._incomingClients[this.localID];
-      let names = new Set([this.localName]);
-      for (let id in this._incomingClients) {
-        let record = this._store._remoteClients[id];
-        if (!names.has(record.name)) {
-          names.add(record.name);
-          continue;
-        }
-        let remoteAge = AsyncResource.serverTime - this._incomingClients[id];
-        if (remoteAge > STALE_CLIENT_REMOTE_AGE) {
-          this._log.info(`Hiding stale client ${id} with age ${remoteAge}`);
-          record.stale = true;
-        }
-      }
-    } finally {
-      this._incomingClients = null;
-    }
-  },
-
-  _uploadOutgoing() {
-    this._currentlySyncingCommands = this._prepareCommandsForUpload();
-    const clientWithPendingCommands = Object.keys(this._currentlySyncingCommands);
-    for (let clientId of clientWithPendingCommands) {
-      if (this._store._remoteClients[clientId] || this.localID == clientId) {
-        this._modified.set(clientId, 0);
-      }
-    }
-    SyncEngine.prototype._uploadOutgoing.call(this);
-  },
-
-  _onRecordsWritten(succeeded, failed) {
-    // Reconcile the status of the local records with what we just wrote on the
-    // server
-    for (let id of succeeded) {
-      const commandChanges = this._currentlySyncingCommands[id];
-      if (id == this.localID) {
-        if (this.localCommands) {
-          this.localCommands = this.localCommands.filter(command => !hasDupeCommand(commandChanges, command));
-        }
-      } else {
-        const clientRecord = this._store._remoteClients[id];
-        if (!commandChanges || !clientRecord) {
-          // should be impossible, else we wouldn't have been writing it.
-          this._log.warn("No command/No record changes for a client we uploaded");
-          continue;
-        }
-        // fixup the client record, so our copy of _remoteClients matches what we uploaded.
-        clientRecord.commands = this._store.createRecord(id);
-        // we could do better and pass the reference to the record we just uploaded,
-        // but this will do for now
-      }
-    }
-
-    // Re-add failed commands
-    for (let id of failed) {
-      const commandChanges = this._currentlySyncingCommands[id];
-      if (!commandChanges) {
-        continue;
-      }
-      this._addClientCommand(id, commandChanges);
-    }
-
-    this._deleteUploadedCommands();
-
-    // Notify other devices that their own client collection changed
-    const idsToNotify = succeeded.reduce((acc, id) => {
-      if (id == this.localID) {
-        return acc;
-      }
-      const fxaDeviceId = this.getClientFxaDeviceId(id);
-      return fxaDeviceId ? acc.concat(fxaDeviceId) : acc;
-    }, []);
-    if (idsToNotify.length > 0) {
-      this._notifyCollectionChanged(idsToNotify);
-    }
-  },
-
-  _notifyCollectionChanged(ids) {
-    const message = {
-      version: 1,
-      command: "sync:collection_changed",
-      data: {
-        collections: ["clients"]
-      }
-    };
-    fxAccounts.notifyDevices(ids, message, NOTIFY_TAB_SENT_TTL_SECS);
-  },
-
-  _syncFinish() {
-    // Record histograms for our device types, and also write them to a pref
-    // so non-histogram telemetry (eg, UITelemetry) has easy access to them.
-    for (let [deviceType, count] of this.deviceTypes) {
-      let hid;
-      let prefName = this.name + ".devices.";
-      switch (deviceType) {
-        case "desktop":
-          hid = "WEAVE_DEVICE_COUNT_DESKTOP";
-          prefName += "desktop";
-          break;
-        case "mobile":
-          hid = "WEAVE_DEVICE_COUNT_MOBILE";
-          prefName += "mobile";
-          break;
-        default:
-          this._log.warn(`Unexpected deviceType "${deviceType}" recording device telemetry.`);
-          continue;
-      }
-      Services.telemetry.getHistogramById(hid).add(count);
-      Svc.Prefs.set(prefName, count);
-    }
-    SyncEngine.prototype._syncFinish.call(this);
-  },
-
-  _reconcile: function _reconcile(item) {
-    // Every incoming record is reconciled, so we use this to track the
-    // contents of the collection on the server.
-    this._incomingClients[item.id] = item.modified;
-
-    if (!this._store.itemExists(item.id)) {
-      return true;
-    }
-    // Clients are synced unconditionally, so we'll always have new records.
-    // Unfortunately, this will cause the scheduler to use the immediate sync
-    // interval for the multi-device case, instead of the active interval. We
-    // work around this by updating the record during reconciliation, and
-    // returning false to indicate that the record doesn't need to be applied
-    // later.
-    this._store.update(item);
-    return false;
+  // Always process incoming items because they might have commands
+  _reconcile: function _reconcile() {
+    return true;
   },
 
   // Treat reset the same as wiping for locally cached clients
@@ -426,13 +148,7 @@ ClientEngine.prototype = {
 
   _wipeClient: function _wipeClient() {
     SyncEngine.prototype._resetClient.call(this);
-    delete this.localCommands;
     this._store.wipe();
-    const logRemoveError = err => this._log.warn("Could not delete json file", err);
-    Async.promiseSpinningly(
-      Utils.jsonRemove("commands", this).catch(logRemoveError)
-        .then(Utils.jsonRemove("commands-syncing", this).catch(logRemoveError))
-    );
   },
 
   removeClientData: function removeClientData() {
@@ -471,6 +187,14 @@ ClientEngine.prototype = {
   },
 
   /**
+   * Remove any commands for the local client and mark it for upload.
+   */
+  clearCommands: function clearCommands() {
+    delete this.localCommands;
+    this._tracker.addChangedID(this.localID);
+  },
+
+  /**
    * Sends a command+args pair to a specific client.
    *
    * @param command Command string
@@ -484,17 +208,30 @@ ClientEngine.prototype = {
     if (!client) {
       throw new Error("Unknown remote client ID: '" + clientId + "'.");
     }
-    if (client.stale) {
-      throw new Error("Stale remote client ID: '" + clientId + "'.");
-    }
+
+    // notDupe compares two commands and returns if they are not equal.
+    let notDupe = function(other) {
+      return other.command != command || !Utils.deepEquals(other.args, args);
+    };
 
     let action = {
       command: command,
       args: args,
     };
 
+    if (!client.commands) {
+      client.commands = [action];
+    }
+    // Add the new action if there are no duplicates.
+    else if (client.commands.every(notDupe)) {
+      client.commands.push(action);
+    }
+    // It must be a dupe. Skip.
+    else {
+      return;
+    }
+
     this._log.trace("Client " + clientId + " got a new action: " + [command, args]);
-    this._addClientCommand(clientId, action);
     this._tracker.addChangedID(clientId);
   },
 
@@ -505,17 +242,13 @@ ClientEngine.prototype = {
    */
   processIncomingCommands: function processIncomingCommands() {
     return this._notify("clients:process-commands", "", function() {
-      if (!this.localCommands) {
-        return true;
-      }
+      let commands = this.localCommands;
 
-      const clearedCommands = this._readCommands()[this.localID];
-      const commands = this.localCommands.filter(command => !hasDupeCommand(clearedCommands, command));
+      // Immediately clear out the commands as we've got them locally.
+      this.clearCommands();
 
-      let URIsToDisplay = [];
       // Process each command in order.
-      for (let rawCommand of commands) {
-        let {command, args} = rawCommand;
+      for each (let {command, args} in commands) {
         this._log.debug("Processing command: " + command + "(" + args + ")");
 
         let engines = [args[0]];
@@ -536,20 +269,12 @@ ClientEngine.prototype = {
             this.service.logout();
             return false;
           case "displayURI":
-            let [uri, clientId, title] = args;
-            URIsToDisplay.push({ uri, clientId, title });
+            this._handleDisplayURI.apply(this, args);
             break;
           default:
             this._log.debug("Received an unknown command: " + command);
             break;
         }
-        // Add the command to the "cleared" commands list
-        this._addClientCommand(this.localID, rawCommand)
-      }
-      this._tracker.addChangedID(this.localID);
-
-      if (URIsToDisplay.length) {
-        this._handleDisplayURIs(URIsToDisplay);
       }
 
       return true;
@@ -588,10 +313,8 @@ ClientEngine.prototype = {
     if (clientId) {
       this._sendCommandToClient(command, args, clientId);
     } else {
-      for (let [id, record] of Object.entries(this._store._remoteClients)) {
-        if (!record.stale) {
-          this._sendCommandToClient(command, args, id);
-        }
+      for (let id in this._store._remoteClients) {
+        this._sendCommandToClient(command, args, id);
       }
     }
   },
@@ -622,11 +345,11 @@ ClientEngine.prototype = {
   },
 
   /**
-   * Handle a bunch of received 'displayURI' commands.
+   * Handle a single received 'displayURI' command.
    *
-   * Interested parties should observe the "weave:engine:clients:display-uris"
-   * topic. The callback will receive an array as the subject parameter
-   * containing objects with the following keys:
+   * Interested parties should observe the "weave:engine:clients:display-uri"
+   * topic. The callback will receive an object as the subject parameter with
+   * the following keys:
    *
    *   uri       URI (string) that is requested for display.
    *   clientId  ID of client that sent the command.
@@ -634,24 +357,21 @@ ClientEngine.prototype = {
    *
    * The 'data' parameter to the callback will not be defined.
    *
-   * @param uris
-   *        An array containing URI objects to display
-   * @param uris[].uri
+   * @param uri
    *        String URI that was received
-   * @param uris[].clientId
+   * @param clientId
    *        ID of client that sent URI
-   * @param uris[].title
+   * @param title
    *        String title of page that URI corresponds to. Older clients may not
    *        send this.
    */
-  _handleDisplayURIs: function _handleDisplayURIs(uris) {
-    Svc.Obs.notify("weave:engine:clients:display-uris", uris);
-  },
+  _handleDisplayURI: function _handleDisplayURI(uri, clientId, title) {
+    this._log.info("Received a URI for display: " + uri + " (" + title +
+                   ") from " + clientId);
 
-  _removeRemoteClient(id) {
-    delete this._store._remoteClients[id];
-    this._tracker.removeChangedID(id);
-  },
+    let subject = {uri: uri, client: clientId, title: title};
+    Svc.Obs.notify("weave:engine:clients:display-uri", subject);
+  }
 };
 
 function ClientStore(name, engine) {
@@ -660,48 +380,29 @@ function ClientStore(name, engine) {
 ClientStore.prototype = {
   __proto__: Store.prototype,
 
-  _remoteClients: {},
-
   create(record) {
-    this.update(record);
+    this.update(record)
   },
 
   update: function update(record) {
-    if (record.id == this.engine.localID) {
-      // Only grab commands from the server; local name/type always wins
+    // Only grab commands from the server; local name/type always wins
+    if (record.id == this.engine.localID)
       this.engine.localCommands = record.commands;
-    } else {
+    else
       this._remoteClients[record.id] = record.cleartext;
-    }
   },
 
   createRecord: function createRecord(id, collection) {
     let record = new ClientsRec(collection, id);
 
-    const commandsChanges = this.engine._currentlySyncingCommands ?
-                            this.engine._currentlySyncingCommands[id] :
-                            [];
-
     // Package the individual components into a record for the local client
     if (id == this.engine.localID) {
-      let cb = Async.makeSpinningCallback();
-      fxAccounts.getDeviceId().then(id => cb(null, id), cb);
-      try {
-        record.fxaDeviceId = cb.wait();
-      } catch(error) {
-        this._log.warn("failed to get fxa device id", error);
-      }
       record.name = this.engine.localName;
       record.type = this.engine.localType;
+      record.commands = this.engine.localCommands;
       record.version = Services.appinfo.version;
       record.protocols = SUPPORTED_PROTOCOL_VERSIONS;
 
-      // Substract the commands we recorded that we've already executed
-      if (commandsChanges && commandsChanges.length &&
-          this.engine.localCommands && this.engine.localCommands.length) {
-        record.commands = this.engine.localCommands.filter(command => !hasDupeCommand(commandsChanges, command));
-      }
-
       // Optional fields.
       record.os = Services.appinfo.OS;             // "Darwin"
       record.appPackage = Services.appinfo.ID;
@@ -712,20 +413,6 @@ ClientStore.prototype = {
       // record.formfactor = "";        // Bug 1100722
     } else {
       record.cleartext = this._remoteClients[id];
-
-      // Add the commands we have to send
-      if (commandsChanges && commandsChanges.length) {
-        const recordCommands = record.cleartext.commands || [];
-        const newCommands = commandsChanges.filter(command => !hasDupeCommand(recordCommands, command));
-        record.cleartext.commands = recordCommands.concat(newCommands);
-      }
-
-      if (record.cleartext.stale) {
-        // It's almost certainly a logic error for us to upload a record we
-        // consider stale, so make log noise, but still remove the flag.
-        this._log.error(`Preparing to upload record ${id} that we consider stale`);
-        delete record.cleartext.stale;
-      }
     }
 
     return record;
@@ -768,7 +455,7 @@ ClientsTracker.prototype = {
         break;
       case "weave:engine:stop-tracking":
         if (this._enabled) {
-          Svc.Prefs.ignore("client.name", this);
+          Svc.Prefs.ignore("clients.name", this);
           this._enabled = false;
         }
         break;
diff --git a/services/sync/modules/engines/forms.js b/services/sync/modules/engines/forms.js
index 43f79d4f7..d26d57176 100644
--- a/services/sync/modules/engines/forms.js
+++ b/services/sync/modules/engines/forms.js
@@ -2,11 +2,11 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-this.EXPORTED_SYMBOLS = ['FormEngine', 'FormRec', 'FormValidator'];
+this.EXPORTED_SYMBOLS = ['FormEngine', 'FormRec'];
 
-var Cc = Components.classes;
-var Ci = Components.interfaces;
-var Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://services-sync/engines.js");
@@ -14,10 +14,9 @@ Cu.import("resource://services-sync/record.js");
 Cu.import("resource://services-common/async.js");
 Cu.import("resource://services-sync/util.js");
 Cu.import("resource://services-sync/constants.js");
-Cu.import("resource://services-sync/collection_validator.js");
 Cu.import("resource://gre/modules/Log.jsm");
 
-const FORMS_TTL = 3 * 365 * 24 * 60 * 60;   // Three years in seconds.
+const FORMS_TTL = 5184000; // 60 days
 
 this.FormRec = function FormRec(collection, id) {
   CryptoWrapper.call(this, collection, id);
@@ -31,30 +30,26 @@ FormRec.prototype = {
 Utils.deferGetSet(FormRec, "cleartext", ["name", "value"]);
 
 
-var FormWrapper = {
+let FormWrapper = {
   _log: Log.repository.getLogger("Sync.Engine.Forms"),
 
   _getEntryCols: ["fieldname", "value"],
   _guidCols:     ["guid"],
 
-  _promiseSearch: function(terms, searchData) {
-    return new Promise(resolve => {
-      let results = [];
-      let callbacks = {
-        handleResult(result) {
-          results.push(result);
-        },
-        handleCompletion(reason) {
-          resolve(results);
-        }
-      };
-      Svc.FormHistory.search(terms, searchData, callbacks);
-    })
-  },
-
   // Do a "sync" search by spinning the event loop until it completes.
   _searchSpinningly: function(terms, searchData) {
-    return Async.promiseSpinningly(this._promiseSearch(terms, searchData));
+    let results = [];
+    let cb = Async.makeSpinningCallback();
+    let callbacks = {
+      handleResult: function(result) {
+        results.push(result);
+      },
+      handleCompletion: function(reason) {
+        cb(null, results);
+      }
+    };
+    Svc.FormHistory.search(terms, searchData, callbacks);
+    return cb.wait();
   },
 
   _updateSpinningly: function(changes) {
@@ -114,9 +109,7 @@ FormEngine.prototype = {
 
   syncPriority: 6,
 
-  get prefName() {
-    return "history";
-  },
+  get prefName() "history",
 
   _findDupe: function _findDupe(item) {
     return FormWrapper.getGUID(item.name, item.value);
@@ -232,9 +225,7 @@ FormTracker.prototype = {
 
   observe: function (subject, topic, data) {
     Tracker.prototype.observe.call(this, subject, topic, data);
-    if (this.ignoreAll) {
-      return;
-    }
+
     switch (topic) {
       case "satchel-storage-changed":
         if (data == "formhistory-add" || data == "formhistory-remove") {
@@ -250,56 +241,3 @@ FormTracker.prototype = {
     this.score += SCORE_INCREMENT_MEDIUM;
   },
 };
-
-
-class FormsProblemData extends CollectionProblemData {
-  getSummary() {
-    // We don't support syncing deleted form data, so "clientMissing" isn't a problem
-    return super.getSummary().filter(entry =>
-      entry.name !== "clientMissing");
-  }
-}
-
-class FormValidator extends CollectionValidator {
-  constructor() {
-    super("forms", "id", ["name", "value"]);
-  }
-
-  emptyProblemData() {
-    return new FormsProblemData();
-  }
-
-  getClientItems() {
-    return FormWrapper._promiseSearch(["guid", "fieldname", "value"], {});
-  }
-
-  normalizeClientItem(item) {
-    return {
-      id: item.guid,
-      guid: item.guid,
-      name: item.fieldname,
-      fieldname: item.fieldname,
-      value: item.value,
-      original: item,
-    };
-  }
-
-  normalizeServerItem(item) {
-    let res = Object.assign({
-      guid: item.id,
-      fieldname: item.name,
-      original: item,
-    }, item);
-    // Missing `name` or `value` causes the getGUID call to throw
-    if (item.name !== undefined && item.value !== undefined) {
-      let guid = FormWrapper.getGUID(item.name, item.value);
-      if (guid) {
-        res.guid = guid;
-        res.id = guid;
-        res.duped = true;
-      }
-    }
-
-    return res;
-  }
-}
\ No newline at end of file
diff --git a/services/sync/modules/engines/history.js b/services/sync/modules/engines/history.js
index 307d484c1..99ecb4506 100644
--- a/services/sync/modules/engines/history.js
+++ b/services/sync/modules/engines/history.js
@@ -4,10 +4,10 @@
 
 this.EXPORTED_SYMBOLS = ['HistoryEngine', 'HistoryRec'];
 
-var Cc = Components.classes;
-var Ci = Components.interfaces;
-var Cu = Components.utils;
-var Cr = Components.results;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+const Cr = Components.results;
 
 const HISTORY_TTL = 5184000; // 60 days
 
@@ -44,25 +44,6 @@ HistoryEngine.prototype = {
   applyIncomingBatchSize: HISTORY_STORE_BATCH_SIZE,
 
   syncPriority: 7,
-
-  _processIncoming: function (newitems) {
-    // We want to notify history observers that a batch operation is underway
-    // so they don't do lots of work for each incoming record.
-    let observers = PlacesUtils.history.getObservers();
-    function notifyHistoryObservers(notification) {
-      for (let observer of observers) {
-        try {
-          observer[notification]();
-        } catch (ex) { }
-      }
-    }
-    notifyHistoryObservers("onBeginUpdateBatch");
-    try {
-      return SyncEngine.prototype._processIncoming.call(this, newitems);
-    } finally {
-      notifyHistoryObservers("onEndUpdateBatch");
-    }
-  },
 };
 
 function HistoryStore(name, engine) {
@@ -70,8 +51,7 @@ function HistoryStore(name, engine) {
 
   // Explicitly nullify our references to our cached services so we don't leak
   Svc.Obs.add("places-shutdown", function() {
-    for (let query in this._stmts) {
-      let stmt = this._stmts;
+    for each ([query, stmt] in Iterator(this._stmts)) {
       stmt.finalize();
     }
     this._stmts = {};
@@ -105,7 +85,7 @@ HistoryStore.prototype = {
     return this._getStmt(
       "UPDATE moz_places " +
       "SET guid = :guid " +
-      "WHERE url_hash = hash(:page_url) AND url = :page_url");
+      "WHERE url = :page_url");
   },
 
   // Some helper functions to handle GUIDs
@@ -127,7 +107,7 @@ HistoryStore.prototype = {
     return this._getStmt(
       "SELECT guid " +
       "FROM moz_places " +
-      "WHERE url_hash = hash(:page_url) AND url = :page_url");
+      "WHERE url = :page_url");
   },
   _guidCols: ["guid"],
 
@@ -146,12 +126,12 @@ HistoryStore.prototype = {
   },
 
   get _visitStm() {
-    return this._getStmt(`/* do not warn (bug 599936) */
-      SELECT visit_type type, visit_date date
-      FROM moz_historyvisits
-      JOIN moz_places h ON h.id = place_id
-      WHERE url_hash = hash(:url) AND url = :url
-      ORDER BY date DESC LIMIT 20`);
+    return this._getStmt(
+      "/* do not warn (bug 599936) */ " +
+      "SELECT visit_type type, visit_date date " +
+      "FROM moz_historyvisits " +
+      "WHERE place_id = (SELECT id FROM moz_places WHERE url = :url) " +
+      "ORDER BY date DESC LIMIT 10");
   },
   _visitCols: ["date", "type"],
 
@@ -223,10 +203,7 @@ HistoryStore.prototype = {
         } else {
           shouldApply = this._recordToPlaceInfo(record);
         }
-      } catch (ex) {
-        if (Async.isShutdownException(ex)) {
-          throw ex;
-        }
+      } catch(ex) {
         failed.push(record.id);
         shouldApply = false;
       }
@@ -299,14 +276,14 @@ HistoryStore.prototype = {
       if (!visit.date || typeof visit.date != "number") {
         this._log.warn("Encountered record with invalid visit date: "
                        + visit.date);
-        continue;
+        throw "Visit has no date!";
       }
 
-      if (!visit.type ||
-          !Object.values(PlacesUtils.history.TRANSITIONS).includes(visit.type)) {
-        this._log.warn("Encountered record with invalid visit type: " +
-                       visit.type + "; ignoring.");
-        continue;
+      if (!visit.type || !(visit.type >= PlacesUtils.history.TRANSITION_LINK &&
+                           visit.type <= PlacesUtils.history.TRANSITION_FRAMED_LINK)) {
+        this._log.warn("Encountered record with invalid visit type: "
+                       + visit.type);
+        throw "Invalid visit type!";
       }
 
       // Dates need to be integers.
@@ -317,7 +294,6 @@ HistoryStore.prototype = {
         // overwritten.
         continue;
       }
-
       visit.visitDate = visit.date;
       visit.transitionType = visit.type;
       k += 1;
@@ -369,9 +345,7 @@ HistoryStore.prototype = {
   },
 
   wipe: function HistStore_wipe() {
-    let cb = Async.makeSyncCallback();
-    PlacesUtils.history.clear().then(result => {cb(null, result)}, err => {cb(err)});
-    return Async.waitForSyncCallback(cb);
+    PlacesUtils.history.removeAllPages();
   }
 };
 
diff --git a/services/sync/modules/engines/passwords.js b/services/sync/modules/engines/passwords.js
index 51db49a0a..994b59767 100644
--- a/services/sync/modules/engines/passwords.js
+++ b/services/sync/modules/engines/passwords.js
@@ -2,16 +2,14 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-this.EXPORTED_SYMBOLS = ['PasswordEngine', 'LoginRec', 'PasswordValidator'];
+this.EXPORTED_SYMBOLS = ['PasswordEngine', 'LoginRec'];
 
-var {classes: Cc, interfaces: Ci, utils: Cu} = Components;
+const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
 
 Cu.import("resource://services-sync/record.js");
 Cu.import("resource://services-sync/constants.js");
-Cu.import("resource://services-sync/collection_validator.js");
 Cu.import("resource://services-sync/engines.js");
 Cu.import("resource://services-sync/util.js");
-Cu.import("resource://services-common/async.js");
 
 this.LoginRec = function LoginRec(collection, id) {
   CryptoWrapper.call(this, collection, id);
@@ -24,7 +22,6 @@ LoginRec.prototype = {
 Utils.deferGetSet(LoginRec, "cleartext", [
     "hostname", "formSubmitURL",
     "httpRealm", "username", "password", "usernameField", "passwordField",
-    "timeCreated", "timePasswordChanged",
     ]);
 
 
@@ -70,10 +67,7 @@ PasswordEngine.prototype = {
         Svc.Prefs.set("deletePwdFxA", true);
         Svc.Prefs.reset("deletePwd"); // The old prefname we previously used.
       } catch (ex) {
-        if (Async.isShutdownException(ex)) {
-          throw ex;
-        }
-        this._log.debug("Password deletes failed", ex);
+        this._log.debug("Password deletes failed: " + Utils.exceptionStr(ex));
       }
     }
   },
@@ -89,7 +83,7 @@ PasswordEngine.prototype = {
     this._store._sleep(0); // Yield back to main thread after synchronous operation.
 
     // Look for existing logins that match the hostname, but ignore the password.
-    for (let local of logins) {
+    for each (let local in logins) {
       if (login.matches(local, true) && local instanceof Ci.nsILoginMetaInfo) {
         return local.guid;
       }
@@ -104,13 +98,6 @@ function PasswordStore(name, engine) {
 PasswordStore.prototype = {
   __proto__: Store.prototype,
 
-  _newPropertyBag: function () {
-    return Cc["@mozilla.org/hash-property-bag;1"].createInstance(Ci.nsIWritablePropertyBag2);
-  },
-
-  /**
-   * Return an instance of nsILoginInfo (and, implicitly, nsILoginMetaInfo).
-   */
   _nsLoginInfoFromRecord: function (record) {
     function nullUndefined(x) {
       return (x == undefined) ? null : x;
@@ -131,21 +118,13 @@ PasswordStore.prototype = {
                                      record.password,
                                      record.usernameField,
                                      record.passwordField);
-
     info.QueryInterface(Ci.nsILoginMetaInfo);
     info.guid = record.id;
-    if (record.timeCreated) {
-      info.timeCreated = record.timeCreated;
-    }
-    if (record.timePasswordChanged) {
-      info.timePasswordChanged = record.timePasswordChanged;
-    }
-
     return info;
   },
 
   _getLoginFromGUID: function (id) {
-    let prop = this._newPropertyBag();
+    let prop = Cc["@mozilla.org/hash-property-bag;1"].createInstance(Ci.nsIWritablePropertyBag2);
     prop.setPropertyAsAUTF8String("guid", id);
 
     let logins = Services.logins.searchLogins({}, prop);
@@ -190,7 +169,8 @@ PasswordStore.prototype = {
       return;
     }
 
-    let prop = this._newPropertyBag();
+    let prop = Cc["@mozilla.org/hash-property-bag;1"]
+                 .createInstance(Ci.nsIWritablePropertyBag2);
     prop.setPropertyAsAUTF8String("guid", newID);
 
     Services.logins.modifyLogin(oldLogin, prop);
@@ -217,11 +197,6 @@ PasswordStore.prototype = {
     record.usernameField = login.usernameField;
     record.passwordField = login.passwordField;
 
-    // Optional fields.
-    login.QueryInterface(Ci.nsILoginMetaInfo);
-    record.timeCreated = login.timeCreated;
-    record.timePasswordChanged = login.timePasswordChanged;
-
     return record;
   },
 
@@ -237,7 +212,8 @@ PasswordStore.prototype = {
     try {
       Services.logins.addLogin(login);
     } catch(ex) {
-      this._log.debug(`Adding record ${record.id} resulted in exception`, ex);
+      this._log.debug("Adding record " + record.id +
+                      " resulted in exception " + Utils.exceptionStr(ex));
     }
   },
 
@@ -269,7 +245,9 @@ PasswordStore.prototype = {
     try {
       Services.logins.modifyLogin(loginItem, newinfo);
     } catch(ex) {
-      this._log.debug(`Modifying record ${record.id} resulted in exception; not modifying`, ex);
+      this._log.debug("Modifying record " + record.id +
+                      " resulted in exception " + Utils.exceptionStr(ex) +
+                      ". Not modifying.");
     }
   },
 
@@ -326,46 +304,3 @@ PasswordTracker.prototype = {
     }
   },
 };
-
-class PasswordValidator extends CollectionValidator {
-  constructor() {
-    super("passwords", "id", [
-      "hostname",
-      "formSubmitURL",
-      "httpRealm",
-      "password",
-      "passwordField",
-      "username",
-      "usernameField",
-    ]);
-  }
-
-  getClientItems() {
-    let logins = Services.logins.getAllLogins({});
-    let syncHosts = Utils.getSyncCredentialsHosts()
-    let result = logins.map(l => l.QueryInterface(Ci.nsILoginMetaInfo))
-                       .filter(l => !syncHosts.has(l.hostname));
-    return Promise.resolve(result);
-  }
-
-  normalizeClientItem(item) {
-    return {
-      id: item.guid,
-      guid: item.guid,
-      hostname: item.hostname,
-      formSubmitURL: item.formSubmitURL,
-      httpRealm: item.httpRealm,
-      password: item.password,
-      passwordField: item.passwordField,
-      username: item.username,
-      usernameField: item.usernameField,
-      original: item,
-    }
-  }
-
-  normalizeServerItem(item) {
-    return Object.assign({ guid: item.id }, item);
-  }
-}
-
-
diff --git a/services/sync/modules/engines/prefs.js b/services/sync/modules/engines/prefs.js
index 9ceeb9ac6..82091d5b4 100644
--- a/services/sync/modules/engines/prefs.js
+++ b/services/sync/modules/engines/prefs.js
@@ -4,11 +4,11 @@
 
 this.EXPORTED_SYMBOLS = ['PrefsEngine', 'PrefRec'];
 
-var Cc = Components.classes;
-var Ci = Components.interfaces;
-var Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
 
-const PREF_SYNC_PREFS_PREFIX = "services.sync.prefs.sync.";
+const SYNC_PREFS_PREFIX = "services.sync.prefs.sync.";
 
 Cu.import("resource://services-sync/engines.js");
 Cu.import("resource://services-sync/record.js");
@@ -42,7 +42,6 @@ PrefsEngine.prototype = {
   version: 2,
 
   syncPriority: 1,
-  allowSkippedRecord: false,
 
   getChangedIDs: function () {
     // No need for a proper timestamp (no conflict resolution needed).
@@ -88,45 +87,37 @@ PrefStore.prototype = {
   _getSyncPrefs: function () {
     let syncPrefs = Cc["@mozilla.org/preferences-service;1"]
                       .getService(Ci.nsIPrefService)
-                      .getBranch(PREF_SYNC_PREFS_PREFIX)
+                      .getBranch(SYNC_PREFS_PREFIX)
                       .getChildList("", {});
     // Also sync preferences that determine which prefs get synced.
-    let controlPrefs = syncPrefs.map(pref => PREF_SYNC_PREFS_PREFIX + pref);
+    let controlPrefs = syncPrefs.map(pref => SYNC_PREFS_PREFIX + pref);
     return controlPrefs.concat(syncPrefs);
   },
 
   _isSynced: function (pref) {
-    return pref.startsWith(PREF_SYNC_PREFS_PREFIX) ||
-           this._prefs.get(PREF_SYNC_PREFS_PREFIX + pref, false);
+    return pref.startsWith(SYNC_PREFS_PREFIX) ||
+            this._prefs.get(SYNC_PREFS_PREFIX + pref, false);
   },
 
   _getAllPrefs: function () {
     let values = {};
-    for (let pref of this._getSyncPrefs()) {
+    for each (let pref in this._getSyncPrefs()) {
       if (this._isSynced(pref)) {
-        // Missing and default prefs get the null value.
-        values[pref] = this._prefs.isSet(pref) ? this._prefs.get(pref, null) : null;
+        // Missing prefs get the null value.
+        values[pref] = this._prefs.get(pref, null);
       }
     }
     return values;
   },
 
-  _updateLightWeightTheme (themeID) {
-    let themeObject = null;
-    if (themeID) {
-      themeObject = LightweightThemeManager.getUsedTheme(themeID);
-    }
-    LightweightThemeManager.currentTheme = themeObject;
-  },
-
   _setAllPrefs: function (values) {
-    let selectedThemeIDPref = "lightweightThemes.selectedThemeID";
-    let selectedThemeIDBefore = this._prefs.get(selectedThemeIDPref, null);
-    let selectedThemeIDAfter = selectedThemeIDBefore;
+    let enabledPref = "lightweightThemes.isThemeSelected";
+    let enabledBefore = this._prefs.get(enabledPref, false);
+    let prevTheme = LightweightThemeManager.currentTheme;
 
     // Update 'services.sync.prefs.sync.foo.pref' before 'foo.pref', otherwise
     // _isSynced returns false when 'foo.pref' doesn't exist (e.g., on a new device).
-    let prefs = Object.keys(values).sort(a => -a.indexOf(PREF_SYNC_PREFS_PREFIX));
+    let prefs = Object.keys(values).sort(a => -a.indexOf(SYNC_PREFS_PREFIX));
     for (let pref of prefs) {
       if (!this._isSynced(pref)) {
         continue;
@@ -134,30 +125,26 @@ PrefStore.prototype = {
 
       let value = values[pref];
 
-      switch (pref) {
-        // Some special prefs we don't want to set directly.
-        case selectedThemeIDPref:
-          selectedThemeIDAfter = value;
-          break;
-
-        // default is to just set the pref
-        default:
-          if (value == null) {
-            // Pref has gone missing. The best we can do is reset it.
-            this._prefs.reset(pref);
-          } else {
-            try {
-              this._prefs.set(pref, value);
-            } catch(ex) {
-              this._log.trace("Failed to set pref: " + pref + ": " + ex);
-            }
-          }
+      // Pref has gone missing. The best we can do is reset it.
+      if (value == null) {
+        this._prefs.reset(pref);
+        continue;
       }
+
+      try {
+        this._prefs.set(pref, value);
+      } catch(ex) {
+        this._log.trace("Failed to set pref: " + pref + ": " + ex);
+      } 
     }
 
-    // Notify the lightweight theme manager if the selected theme has changed.
-    if (selectedThemeIDBefore != selectedThemeIDAfter) {
-      this._updateLightWeightTheme(selectedThemeIDAfter);
+    // Notify the lightweight theme manager of all the new values
+    let enabledNow = this._prefs.get(enabledPref, false);
+    if (enabledBefore && !enabledNow) {
+      LightweightThemeManager.currentTheme = null;
+    } else if (enabledNow && LightweightThemeManager.usedThemes[0] != prevTheme) {
+      LightweightThemeManager.currentTheme = null;
+      LightweightThemeManager.currentTheme = LightweightThemeManager.usedThemes[0];
     }
   },
 
@@ -261,8 +248,8 @@ PrefTracker.prototype = {
       case "nsPref:changed":
         // Trigger a sync for MULTI-DEVICE for a change that determines
         // which prefs are synced or a regular pref change.
-        if (data.indexOf(PREF_SYNC_PREFS_PREFIX) == 0 ||
-            this._prefs.get(PREF_SYNC_PREFS_PREFIX + data, false)) {
+        if (data.indexOf(SYNC_PREFS_PREFIX) == 0 ||
+            this._prefs.get(SYNC_PREFS_PREFIX + data, false)) {
           this.score += SCORE_INCREMENT_XLARGE;
           this.modified = true;
           this._log.trace("Preference " + data + " changed");
diff --git a/services/sync/modules/engines/tabs.js b/services/sync/modules/engines/tabs.js
index 45ece4a23..1fce737d2 100644
--- a/services/sync/modules/engines/tabs.js
+++ b/services/sync/modules/engines/tabs.js
@@ -4,7 +4,7 @@
 
 this.EXPORTED_SYMBOLS = ["TabEngine", "TabSetRecord"];
 
-var {classes: Cc, interfaces: Ci, utils: Cu} = Components;
+const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
 
 const TABS_TTL = 604800;           // 7 days.
 const TAB_ENTRIES_LIMIT = 25;      // How many URLs to include in tab history.
@@ -43,11 +43,6 @@ TabEngine.prototype = {
   _storeObj: TabStore,
   _trackerObj: TabTracker,
   _recordObj: TabSetRecord,
-  // A flag to indicate if we have synced in this session. This is to help
-  // consumers of remote tabs that may want to differentiate between "I've an
-  // empty tab list as I haven't yet synced" vs "I've an empty tab list
-  // as there really are no tabs"
-  hasSyncedThisSession: false,
 
   syncPriority: 3,
 
@@ -72,7 +67,6 @@ TabEngine.prototype = {
     SyncEngine.prototype._resetClient.call(this);
     this._store.wipe();
     this._tracker.modified = true;
-    this.hasSyncedThisSession = false;
   },
 
   removeClientData: function () {
@@ -100,12 +94,7 @@ TabEngine.prototype = {
     }
 
     return SyncEngine.prototype._reconcile.call(this, item);
-  },
-
-  _syncFinish() {
-    this.hasSyncedThisSession = true;
-    return SyncEngine.prototype._syncFinish.call(this);
-  },
+  }
 };
 
 
@@ -145,7 +134,7 @@ TabStore.prototype = {
       }
 
       for (let tab of win.gBrowser.tabs) {
-        let tabState = this.getTabState(tab);
+        tabState = this.getTabState(tab);
 
         // Make sure there are history entries to look at.
         if (!tabState || !tabState.entries.length) {
@@ -165,11 +154,6 @@ TabStore.prototype = {
           continue;
         }
 
-        if (current.url.length >= (MAX_UPLOAD_BYTES - 1000)) {
-          this._log.trace("Skipping over-long URL.");
-          continue;
-        }
-
         // The element at `index` is the current page. Previous URLs were
         // previously visited URLs; subsequent URLs are in the 'forward' stack,
         // which we can't represent in Sync, so we truncate here.
@@ -189,9 +173,7 @@ TabStore.prototype = {
         allTabs.push({
           title: current.title || "",
           urlHistory: urls,
-          icon: tabState.image ||
-                (tabState.attributes && tabState.attributes.image) ||
-                "",
+          icon: tabState.attributes && tabState.attributes.image || "",
           lastUsed: Math.floor((tabState.lastAccessed || 0) / 1000),
         });
       }
@@ -265,9 +247,27 @@ TabStore.prototype = {
 
   create: function (record) {
     this._log.debug("Adding remote tabs from " + record.clientName);
-    this._remoteClients[record.id] = Object.assign({}, record.cleartext, {
-      lastModified: record.modified
-    });
+    this._remoteClients[record.id] = record.cleartext;
+
+    // Lose some precision, but that's good enough (seconds).
+    let roundModify = Math.floor(record.modified / 1000);
+    let notifyState = Svc.Prefs.get("notifyTabState");
+
+    // If there's no existing pref, save this first modified time.
+    if (notifyState == null) {
+      Svc.Prefs.set("notifyTabState", roundModify);
+      return;
+    }
+
+    // Don't change notifyState if it's already 0 (don't notify).
+    if (notifyState == 0) {
+      return;
+    }
+
+    // We must have gotten a new tab that isn't the same as last time.
+    if (notifyState != roundModify) {
+      Svc.Prefs.set("notifyTabState", 0);
+    }
   },
 
   update: function (record) {
@@ -302,14 +302,10 @@ TabTracker.prototype = {
 
   _registerListenersForWindow: function (window) {
     this._log.trace("Registering tab listeners in window");
-    for (let topic of this._topics) {
+    for each (let topic in this._topics) {
       window.addEventListener(topic, this.onTab, false);
     }
     window.addEventListener("unload", this._unregisterListeners, false);
-    // If it's got a tab browser we can listen for things like navigation.
-    if (window.gBrowser) {
-      window.gBrowser.addProgressListener(this);
-    }
   },
 
   _unregisterListeners: function (event) {
@@ -319,12 +315,9 @@ TabTracker.prototype = {
   _unregisterListenersForWindow: function (window) {
     this._log.trace("Removing tab listeners in window");
     window.removeEventListener("unload", this._unregisterListeners, false);
-    for (let topic of this._topics) {
+    for each (let topic in this._topics) {
       window.removeEventListener(topic, this.onTab, false);
     }
-    if (window.gBrowser) {
-      window.gBrowser.removeProgressListener(this);
-    }
   },
 
   startTracking: function () {
@@ -380,14 +373,4 @@ TabTracker.prototype = {
       this.score += SCORE_INCREMENT_SMALL;
     }
   },
-
-  // web progress listeners.
-  onLocationChange: function (webProgress, request, location, flags) {
-    // We only care about top-level location changes which are not in the same
-    // document.
-    if (webProgress.isTopLevel &&
-        ((flags & Ci.nsIWebProgressListener.LOCATION_CHANGE_SAME_DOCUMENT) == 0)) {
-      this.modified = true;
-    }
-  },
 };
diff --git a/services/sync/modules/healthreport.jsm b/services/sync/modules/healthreport.jsm
new file mode 100644
index 000000000..47161c095
--- /dev/null
+++ b/services/sync/modules/healthreport.jsm
@@ -0,0 +1,262 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "SyncProvider",
+];
+
+const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
+
+Cu.import("resource://gre/modules/Metrics.jsm", this);
+Cu.import("resource://gre/modules/Promise.jsm", this);
+Cu.import("resource://gre/modules/Services.jsm", this);
+Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
+
+const DAILY_LAST_NUMERIC_FIELD = {type: Metrics.Storage.FIELD_DAILY_LAST_NUMERIC};
+const DAILY_LAST_TEXT_FIELD = {type: Metrics.Storage.FIELD_DAILY_LAST_TEXT};
+const DAILY_COUNTER_FIELD = {type: Metrics.Storage.FIELD_DAILY_COUNTER};
+
+XPCOMUtils.defineLazyModuleGetter(this, "Weave",
+                                  "resource://services-sync/main.js");
+
+function SyncMeasurement1() {
+  Metrics.Measurement.call(this);
+}
+
+SyncMeasurement1.prototype = Object.freeze({
+  __proto__: Metrics.Measurement.prototype,
+
+  name: "sync",
+  version: 1,
+
+  fields: {
+    enabled: DAILY_LAST_NUMERIC_FIELD,
+    preferredProtocol: DAILY_LAST_TEXT_FIELD,
+    activeProtocol: DAILY_LAST_TEXT_FIELD,
+    syncStart: DAILY_COUNTER_FIELD,
+    syncSuccess: DAILY_COUNTER_FIELD,
+    syncError: DAILY_COUNTER_FIELD,
+  },
+});
+
+function SyncDevicesMeasurement1() {
+  Metrics.Measurement.call(this);
+}
+
+SyncDevicesMeasurement1.prototype = Object.freeze({
+  __proto__: Metrics.Measurement.prototype,
+
+  name: "devices",
+  version: 1,
+
+  fields: {},
+
+  shouldIncludeField: function (name) {
+    return true;
+  },
+
+  fieldType: function (name) {
+    return Metrics.Storage.FIELD_DAILY_COUNTER;
+  },
+});
+
+function SyncMigrationMeasurement1() {
+  Metrics.Measurement.call(this);
+}
+
+SyncMigrationMeasurement1.prototype = Object.freeze({
+  __proto__: Metrics.Measurement.prototype,
+
+  name: "migration",
+  version: 1,
+
+  fields: {
+    state: DAILY_LAST_TEXT_FIELD, // last "user" or "internal" state we saw for the day
+    accepted: DAILY_COUNTER_FIELD, // number of times user tried to start migration
+    declined: DAILY_COUNTER_FIELD, // number of times user closed nagging infobar
+    unlinked: DAILY_LAST_NUMERIC_FIELD, // did the user decline and unlink
+  },
+});
+
+this.SyncProvider = function () {
+  Metrics.Provider.call(this);
+};
+SyncProvider.prototype = Object.freeze({
+  __proto__: Metrics.Provider.prototype,
+
+  name: "org.mozilla.sync",
+
+  measurementTypes: [
+    SyncDevicesMeasurement1,
+    SyncMeasurement1,
+    SyncMigrationMeasurement1,
+  ],
+
+  _OBSERVERS: [
+    "weave:service:sync:start",
+    "weave:service:sync:finish",
+    "weave:service:sync:error",
+    "fxa-migration:state-changed",
+    "fxa-migration:internal-state-changed",
+    "fxa-migration:internal-telemetry",
+  ],
+
+  postInit: function () {
+    for (let o of this._OBSERVERS) {
+      Services.obs.addObserver(this, o, false);
+    }
+
+    return Promise.resolve();
+  },
+
+  onShutdown: function () {
+    for (let o of this._OBSERVERS) {
+      Services.obs.removeObserver(this, o);
+    }
+
+    return Promise.resolve();
+  },
+
+  observe: function (subject, topic, data) {
+    switch (topic) {
+      case "weave:service:sync:start":
+      case "weave:service:sync:finish":
+      case "weave:service:sync:error":
+        return this._observeSync(subject, topic, data);
+
+      case "fxa-migration:state-changed":
+      case "fxa-migration:internal-state-changed":
+      case "fxa-migration:internal-telemetry":
+        return this._observeMigration(subject, topic, data);
+    }
+    Cu.reportError("unexpected topic in sync healthreport provider: " + topic);
+  },
+
+  _observeSync: function (subject, topic, data) {
+    let field;
+    switch (topic) {
+      case "weave:service:sync:start":
+        field = "syncStart";
+        break;
+
+      case "weave:service:sync:finish":
+        field = "syncSuccess";
+        break;
+
+      case "weave:service:sync:error":
+        field = "syncError";
+        break;
+
+      default:
+        Cu.reportError("unexpected sync topic in sync healthreport provider: " + topic);
+        return;
+    }
+
+    let m = this.getMeasurement(SyncMeasurement1.prototype.name,
+                                SyncMeasurement1.prototype.version);
+    return this.enqueueStorageOperation(function recordSyncEvent() {
+      return m.incrementDailyCounter(field);
+    });
+  },
+
+  _observeMigration: function(subject, topic, data) {
+    switch (topic) {
+      case "fxa-migration:state-changed":
+      case "fxa-migration:internal-state-changed": {
+        // We record both "user" and "internal" states in the same field.  This
+        // works for us as user state is always null when there is an internal
+        // state.
+        if (!data) {
+          return; // we don't count the |null| state
+        }
+        let m = this.getMeasurement(SyncMigrationMeasurement1.prototype.name,
+                                    SyncMigrationMeasurement1.prototype.version);
+        return this.enqueueStorageOperation(function() {
+          return m.setDailyLastText("state", data);
+        });
+      }
+
+      case "fxa-migration:internal-telemetry": {
+        // |data| is our field name.
+        let m = this.getMeasurement(SyncMigrationMeasurement1.prototype.name,
+                                    SyncMigrationMeasurement1.prototype.version);
+        return this.enqueueStorageOperation(function() {
+          switch (data) {
+            case "accepted":
+            case "declined":
+              return m.incrementDailyCounter(data);
+            case "unlinked":
+              return m.setDailyLastNumeric(data, 1);
+            default:
+              Cu.reportError("Unexpected migration field in sync healthreport provider: " + data);
+              return Promise.resolve();
+          }
+        });
+      }
+
+      default:
+        Cu.reportError("unexpected migration topic in sync healthreport provider: " + topic);
+        return;
+    }
+  },
+
+  collectDailyData: function () {
+    return this.storage.enqueueTransaction(this._populateDailyData.bind(this));
+  },
+
+  _populateDailyData: function* () {
+    let m = this.getMeasurement(SyncMeasurement1.prototype.name,
+                                SyncMeasurement1.prototype.version);
+
+    let svc = Cc["@mozilla.org/weave/service;1"]
+                .getService(Ci.nsISupports)
+                .wrappedJSObject;
+
+    let enabled = svc.enabled;
+    yield m.setDailyLastNumeric("enabled", enabled ? 1 : 0);
+
+    // preferredProtocol is constant and only changes as the client
+    // evolves.
+    yield m.setDailyLastText("preferredProtocol", "1.5");
+
+    let protocol = svc.fxAccountsEnabled ? "1.5" : "1.1";
+    yield m.setDailyLastText("activeProtocol", protocol);
+
+    if (!enabled) {
+      return;
+    }
+
+    // Before grabbing more information, be sure the Sync service
+    // is fully initialized. This has the potential to initialize
+    // Sync on the spot. This may be undesired if Sync appears to
+    // be enabled but it really isn't. That responsibility should
+    // be up to svc.enabled to not return false positives, however.
+    yield svc.whenLoaded();
+
+    if (Weave.Status.service != Weave.STATUS_OK) {
+      return;
+    }
+
+    // Device types are dynamic. So we need to dynamically create fields if
+    // they don't exist.
+    let dm = this.getMeasurement(SyncDevicesMeasurement1.prototype.name,
+                                 SyncDevicesMeasurement1.prototype.version);
+    let devices = Weave.Service.clientsEngine.deviceTypes;
+    for (let [field, count] of devices) {
+      let hasField = this.storage.hasFieldFromMeasurement(dm.id, field,
+                                    this.storage.FIELD_DAILY_LAST_NUMERIC);
+      let fieldID;
+      if (hasField) {
+        fieldID = this.storage.fieldIDFromMeasurement(dm.id, field);
+      } else {
+        fieldID = yield this.storage.registerField(dm.id, field,
+                                       this.storage.FIELD_DAILY_LAST_NUMERIC);
+      }
+
+      yield this.storage.setDailyLastNumericFromFieldID(fieldID, count);
+    }
+  },
+});
diff --git a/services/sync/modules/identity.js b/services/sync/modules/identity.js
index b4da8c0bb..2bee13b5b 100644
--- a/services/sync/modules/identity.js
+++ b/services/sync/modules/identity.js
@@ -6,14 +6,13 @@
 
 this.EXPORTED_SYMBOLS = ["IdentityManager"];
 
-var {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Promise.jsm");
 Cu.import("resource://services-sync/constants.js");
 Cu.import("resource://gre/modules/Log.jsm");
 Cu.import("resource://services-sync/util.js");
-Cu.import("resource://services-common/async.js");
 
 // Lazy import to prevent unnecessary load on startup.
 for (let symbol of ["BulkKeyBundle", "SyncKeyBundle"]) {
@@ -85,14 +84,18 @@ IdentityManager.prototype = {
   _syncKeyBundle: null,
 
   /**
-   * Initialize the identity provider.
+   * Initialize the identity provider.  Returns a promise that is resolved
+   * when initialization is complete and the provider can be queried for
+   * its state
    */
   initialize: function() {
     // Nothing to do for this identity provider.
+    return Promise.resolve();
   },
 
   finalize: function() {
     // Nothing to do for this identity provider.
+    return Promise.resolve();
   },
 
   /**
@@ -111,6 +114,14 @@ IdentityManager.prototype = {
     return Promise.resolve();
   },
 
+  /**
+   * Indicates if the identity manager is still initializing
+   */
+  get readyToAuthenticate() {
+    // We initialize in a fully sync manner, so we are always finished.
+    return true;
+  },
+
   get account() {
     return Svc.Prefs.get("account", this.username);
   },
@@ -195,7 +206,7 @@ IdentityManager.prototype = {
         return null;
       }
 
-      for (let login of this._getLogins(PWDMGR_PASSWORD_REALM)) {
+      for each (let login in this._getLogins(PWDMGR_PASSWORD_REALM)) {
         if (login.username.toLowerCase() == username) {
           // It should already be UTF-8 encoded, but we don't take any chances.
           this._basicPassword = Utils.encodeUTF8(login.password);
@@ -249,7 +260,7 @@ IdentityManager.prototype = {
         return null;
       }
 
-      for (let login of this._getLogins(PWDMGR_PASSPHRASE_REALM)) {
+      for each (let login in this._getLogins(PWDMGR_PASSPHRASE_REALM)) {
         if (login.username.toLowerCase() == username) {
           this._syncKey = login.password;
         }
@@ -326,7 +337,7 @@ IdentityManager.prototype = {
       try {
         this._syncKeyBundle = new SyncKeyBundle(this.username, this.syncKey);
       } catch (ex) {
-        this._log.warn("Failed to create sync bundle", ex);
+        this._log.warn(Utils.exceptionStr(ex));
         return null;
       }
     }
@@ -400,7 +411,7 @@ IdentityManager.prototype = {
         this._setLogin(PWDMGR_PASSWORD_REALM, this.username,
                        this._basicPassword);
       } else {
-        for (let login of this._getLogins(PWDMGR_PASSWORD_REALM)) {
+        for each (let login in this._getLogins(PWDMGR_PASSWORD_REALM)) {
           Services.logins.removeLogin(login);
         }
       }
@@ -412,7 +423,7 @@ IdentityManager.prototype = {
       if (this._syncKey) {
         this._setLogin(PWDMGR_PASSPHRASE_REALM, this.username, this._syncKey);
       } else {
-        for (let login of this._getLogins(PWDMGR_PASSPHRASE_REALM)) {
+        for each (let login in this._getLogins(PWDMGR_PASSPHRASE_REALM)) {
           Services.logins.removeLogin(login);
         }
       }
@@ -447,9 +458,6 @@ IdentityManager.prototype = {
     try {
       service.recordManager.get(service.storageURL + "meta/fxa_credentials");
     } catch (ex) {
-      if (Async.isShutdownException(ex)) {
-        throw ex;
-      }
       this._log.warn("Failed to pre-fetch the migration sentinel", ex);
     }
   },
@@ -469,7 +477,7 @@ IdentityManager.prototype = {
    */
   _setLogin: function _setLogin(realm, username, password) {
     let exists = false;
-    for (let login of this._getLogins(realm)) {
+    for each (let login in this._getLogins(realm)) {
       if (login.username == username && login.password == password) {
         exists = true;
       } else {
@@ -505,7 +513,7 @@ IdentityManager.prototype = {
   deleteSyncCredentials: function deleteSyncCredentials() {
     for (let host of this._getSyncCredentialsHosts()) {
       let logins = Services.logins.findLogins({}, host, "", "");
-      for (let login of logins) {
+      for each (let login in logins) {
         Services.logins.removeLogin(login);
       }
     }
@@ -593,13 +601,4 @@ IdentityManager.prototype = {
     // Do nothing for Sync 1.1.
     return {accepted: true};
   },
-
-  // Tell Sync what the login status should be if it saw a 401 fetching
-  // info/collections as part of login verification (typically immediately
-  // after login.)
-  // In our case it means an authoritative "password is incorrect".
-  loginStatusFromVerification404() {
-    return LOGIN_FAILED_LOGIN_REJECTED;
-  }
-
 };
diff --git a/services/sync/modules/jpakeclient.js b/services/sync/modules/jpakeclient.js
index 625dc91b6..10f405371 100644
--- a/services/sync/modules/jpakeclient.js
+++ b/services/sync/modules/jpakeclient.js
@@ -4,7 +4,7 @@
 
 this.EXPORTED_SYMBOLS = ["JPAKEClient", "SendCredentialsController"];
 
-var {classes: Cc, interfaces: Ci, results: Cr, utils: Cu} = Components;
+const {classes: Cc, interfaces: Ci, results: Cr, utils: Cu} = Components;
 
 Cu.import("resource://gre/modules/Log.jsm");
 Cu.import("resource://services-common/rest.js");
@@ -281,7 +281,8 @@ JPAKEClient.prototype = {
     let rng = Cc["@mozilla.org/security/random-generator;1"]
                 .createInstance(Ci.nsIRandomGenerator);
     let bytes = rng.generateRandomBytes(JPAKE_LENGTH_CLIENTID / 2);
-    this._clientID = bytes.map(byte => ("0" + byte.toString(16)).slice(-2)).join("");
+    this._clientID = [("0" + byte.toString(16)).slice(-2)
+                      for each (byte in bytes)].join("");
   },
 
   _createSecret: function _createSecret() {
@@ -290,7 +291,8 @@ JPAKEClient.prototype = {
     let rng = Cc["@mozilla.org/security/random-generator;1"]
                 .createInstance(Ci.nsIRandomGenerator);
     let bytes = rng.generateRandomBytes(JPAKE_LENGTH_SECRET);
-    return bytes.map(byte => key[Math.floor(byte * key.length / 256)]).join("");
+    return [key[Math.floor(byte * key.length / 256)]
+            for each (byte in bytes)].join("");
   },
 
   _newRequest: function _newRequest(uri) {
diff --git a/services/sync/modules/keys.js b/services/sync/modules/keys.js
index b93de7f31..bf909bdc2 100644
--- a/services/sync/modules/keys.js
+++ b/services/sync/modules/keys.js
@@ -9,7 +9,7 @@ this.EXPORTED_SYMBOLS = [
   "SyncKeyBundle"
 ];
 
-var {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
 
 Cu.import("resource://services-sync/constants.js");
 Cu.import("resource://gre/modules/Log.jsm");
diff --git a/services/sync/modules/main.js b/services/sync/modules/main.js
index e8e705e72..488a2594b 100644
--- a/services/sync/modules/main.js
+++ b/services/sync/modules/main.js
@@ -6,7 +6,7 @@ this.EXPORTED_SYMBOLS = ['Weave'];
 
 this.Weave = {};
 Components.utils.import("resource://services-sync/constants.js", Weave);
-var lazies = {
+let lazies = {
   "jpakeclient.js":       ["JPAKEClient", "SendCredentialsController"],
   "notifications.js":     ["Notifications", "Notification", "NotificationButton"],
   "service.js":           ["Service"],
@@ -15,14 +15,12 @@ var lazies = {
 };
 
 function lazyImport(module, dest, props) {
-  function getter(prop) {
-    return function() {
-      let ns = {};
-      Components.utils.import(module, ns);
-      delete dest[prop];
-      return dest[prop] = ns[prop];
-    };
-  }
+  function getter(prop) function() {
+    let ns = {};
+    Components.utils.import(module, ns);
+    delete dest[prop];
+    return dest[prop] = ns[prop];
+  };
   props.forEach(function (prop) { dest.__defineGetter__(prop, getter(prop)); });
 }
 
diff --git a/services/sync/modules/notifications.js b/services/sync/modules/notifications.js
index 72187a4ce..1ee24f2cd 100644
--- a/services/sync/modules/notifications.js
+++ b/services/sync/modules/notifications.js
@@ -4,10 +4,10 @@
 
 this.EXPORTED_SYMBOLS = ["Notifications", "Notification", "NotificationButton"];
 
-var Cc = Components.classes;
-var Ci = Components.interfaces;
-var Cr = Components.results;
-var Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+const Cu = Components.utils;
 
 Cu.import("resource://services-common/observers.js");
 Cu.import("resource://gre/modules/Log.jsm");
diff --git a/services/sync/modules/policies.js b/services/sync/modules/policies.js
index a3933426d..d799cb235 100644
--- a/services/sync/modules/policies.js
+++ b/services/sync/modules/policies.js
@@ -7,26 +7,16 @@ this.EXPORTED_SYMBOLS = [
   "SyncScheduler",
 ];
 
-var {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
 
 Cu.import("resource://gre/modules/Log.jsm");
 Cu.import("resource://services-sync/constants.js");
 Cu.import("resource://services-sync/engines.js");
 Cu.import("resource://services-sync/util.js");
 Cu.import("resource://services-common/logmanager.js");
-Cu.import("resource://services-common/async.js");
 
 XPCOMUtils.defineLazyModuleGetter(this, "Status",
                                   "resource://services-sync/status.js");
-XPCOMUtils.defineLazyModuleGetter(this, "AddonManager",
-                                  "resource://gre/modules/AddonManager.jsm");
-
-// Get the value for an interval that's stored in preferences. To save users
-// from themselves (and us from them!) the minimum time they can specify
-// is 60s.
-function getThrottledIntervalPreference(prefName) {
-  return Math.max(Svc.Prefs.get(prefName), 60) * 1000;
-}
 
 this.SyncScheduler = function SyncScheduler(service) {
   this.service = service;
@@ -55,12 +45,12 @@ SyncScheduler.prototype = {
 
     let part = service.fxAccountsEnabled ? "fxa" : "sync11";
     let prefSDInterval = "scheduler." + part + ".singleDeviceInterval";
-    this.singleDeviceInterval = getThrottledIntervalPreference(prefSDInterval);
+    this.singleDeviceInterval = Svc.Prefs.get(prefSDInterval) * 1000;
 
-    this.idleInterval         = getThrottledIntervalPreference("scheduler.idleInterval");
-    this.activeInterval       = getThrottledIntervalPreference("scheduler.activeInterval");
-    this.immediateInterval    = getThrottledIntervalPreference("scheduler.immediateInterval");
-    this.eolInterval          = getThrottledIntervalPreference("scheduler.eolInterval");
+    this.idleInterval         = Svc.Prefs.get("scheduler.idleInterval")         * 1000;
+    this.activeInterval       = Svc.Prefs.get("scheduler.activeInterval")       * 1000;
+    this.immediateInterval    = Svc.Prefs.get("scheduler.immediateInterval")    * 1000;
+    this.eolInterval          = Svc.Prefs.get("scheduler.eolInterval")          * 1000;
 
     // A user is non-idle on startup by default.
     this.idle = false;
@@ -71,40 +61,20 @@ SyncScheduler.prototype = {
   },
 
   // nextSync is in milliseconds, but prefs can't hold that much
-  get nextSync() {
-    return Svc.Prefs.get("nextSync", 0) * 1000;
-  },
-  set nextSync(value) {
-    Svc.Prefs.set("nextSync", Math.floor(value / 1000));
-  },
+  get nextSync() Svc.Prefs.get("nextSync", 0) * 1000,
+  set nextSync(value) Svc.Prefs.set("nextSync", Math.floor(value / 1000)),
 
-  get syncInterval() {
-    return Svc.Prefs.get("syncInterval", this.singleDeviceInterval);
-  },
-  set syncInterval(value) {
-    Svc.Prefs.set("syncInterval", value);
-  },
+  get syncInterval() Svc.Prefs.get("syncInterval", this.singleDeviceInterval),
+  set syncInterval(value) Svc.Prefs.set("syncInterval", value),
 
-  get syncThreshold() {
-    return Svc.Prefs.get("syncThreshold", SINGLE_USER_THRESHOLD);
-  },
-  set syncThreshold(value) {
-    Svc.Prefs.set("syncThreshold", value);
-  },
+  get syncThreshold() Svc.Prefs.get("syncThreshold", SINGLE_USER_THRESHOLD),
+  set syncThreshold(value) Svc.Prefs.set("syncThreshold", value),
 
-  get globalScore() {
-    return Svc.Prefs.get("globalScore", 0);
-  },
-  set globalScore(value) {
-    Svc.Prefs.set("globalScore", value);
-  },
+  get globalScore() Svc.Prefs.get("globalScore", 0),
+  set globalScore(value) Svc.Prefs.set("globalScore", value),
 
-  get numClients() {
-    return Svc.Prefs.get("numClients", 0);
-  },
-  set numClients(value) {
-    Svc.Prefs.set("numClients", value);
-  },
+  get numClients() Svc.Prefs.get("numClients", 0),
+  set numClients(value) Svc.Prefs.set("numClients", value),
 
   init: function init() {
     this._log.level = Log.Level[Svc.Prefs.get("log.logger.service.main")];
@@ -249,10 +219,7 @@ SyncScheduler.prototype = {
          this.setDefaults();
          try {
            Svc.Idle.removeIdleObserver(this, Svc.Prefs.get("scheduler.idleTime"));
-         } catch (ex) {
-           if (ex.result != Cr.NS_ERROR_FAILURE) {
-             throw ex;
-           }
+         } catch (ex if (ex.result == Cr.NS_ERROR_FAILURE)) {
            // In all likelihood we didn't have an idle observer registered yet.
            // It's all good.
          }
@@ -285,11 +252,10 @@ SyncScheduler.prototype = {
       case "wake_notification":
         this._log.debug("Woke from sleep.");
         Utils.nextTick(() => {
-          // Trigger a sync if we have multiple clients. We give it 5 seconds
-          // incase the network is still in the process of coming back up.
+          // Trigger a sync if we have multiple clients.
           if (this.numClients > 1) {
-            this._log.debug("More than 1 client. Will sync in 5s.");
-            this.scheduleNextSync(5000);
+            this._log.debug("More than 1 client. Syncing.");
+            this.scheduleNextSync(0);
           }
         });
         break;
@@ -531,6 +497,45 @@ SyncScheduler.prototype = {
       this.syncTimer.clear();
   },
 
+  /**
+   * Prevent new syncs from starting.  This is used by the FxA migration code
+   * where we can't afford to have a sync start partway through the migration.
+   * To handle the edge-case of a sync starting and not stopping, we store
+   * this state in a pref, so on the next startup we remain blocked (and thus
+   * sync will never start) so the migration can complete.
+   *
+   * As a safety measure, we only block for some period of time, and after
+   * that it will automatically unblock.  This ensures that if things go
+   * really pear-shaped and we never end up calling unblockSync() we haven't
+   * completely broken the world.
+   */
+  blockSync: function(until = null) {
+    if (!until) {
+      until = Date.now() + DEFAULT_BLOCK_PERIOD;
+    }
+    // until is specified in ms, but Prefs can't hold that much
+    Svc.Prefs.set("scheduler.blocked-until", Math.floor(until / 1000));
+  },
+
+  unblockSync: function() {
+    Svc.Prefs.reset("scheduler.blocked-until");
+    // the migration code should be ready to roll, so resume normal operations.
+    this.checkSyncStatus();
+  },
+
+  get isBlocked() {
+    let until = Svc.Prefs.get("scheduler.blocked-until");
+    if (until === undefined) {
+      return false;
+    }
+    if (until <= Math.floor(Date.now() / 1000)) {
+      // we were previously blocked but the time has expired.
+      Svc.Prefs.reset("scheduler.blocked-until");
+      return false;
+    }
+    // we remain blocked.
+    return true;
+  },
 };
 
 this.ErrorHandler = function ErrorHandler(service) {
@@ -570,10 +575,7 @@ ErrorHandler.prototype = {
     root.level = Log.Level[Svc.Prefs.get("log.rootLogger")];
 
     let logs = ["Sync", "FirefoxAccounts", "Hawk", "Common.TokenServerClient",
-                "Sync.SyncMigration", "browserwindow.syncui",
-                "Services.Common.RESTRequest", "Services.Common.RESTRequest",
-                "BookmarkSyncUtils"
-               ];
+                "Sync.SyncMigration"];
 
     this._logManager = new LogManager(Svc.Prefs, logs, "sync");
   },
@@ -590,25 +592,17 @@ ErrorHandler.prototype = {
           this._log.debug(data + " failed to apply some records.");
         }
         break;
-      case "weave:engine:sync:error": {
+      case "weave:engine:sync:error":
         let exception = subject;  // exception thrown by engine's sync() method
         let engine_name = data;   // engine name that threw the exception
 
         this.checkServerError(exception);
 
         Status.engines = [engine_name, exception.failureCode || ENGINE_UNKNOWN_FAIL];
-        if (Async.isShutdownException(exception)) {
-          this._log.debug(engine_name + " was interrupted due to the application shutting down");
-        } else {
-          this._log.debug(engine_name + " failed", exception);
-          Services.telemetry.getKeyedHistogramById("WEAVE_ENGINE_SYNC_ERRORS")
-                            .add(engine_name);
-        }
+        this._log.debug(engine_name + " failed: " + Utils.exceptionStr(exception));
         break;
-      }
       case "weave:service:login:error":
-        this._log.error("Sync encountered a login error");
-        this.resetFileLog();
+        this.resetFileLog(this._logManager.REASON_ERROR);
 
         if (this.shouldReportError()) {
           this.notifyOnNextTick("weave:ui:login:error");
@@ -618,23 +612,12 @@ ErrorHandler.prototype = {
 
         this.dontIgnoreErrors = false;
         break;
-      case "weave:service:sync:error": {
+      case "weave:service:sync:error":
         if (Status.sync == CREDENTIALS_CHANGED) {
           this.service.logout();
         }
 
-        let exception = subject;
-        if (Async.isShutdownException(exception)) {
-          // If we are shutting down we just log the fact, attempt to flush
-          // the log file and get out of here!
-          this._log.error("Sync was interrupted due to the application shutting down");
-          this.resetFileLog();
-          break;
-        }
-
-        // Not a shutdown related exception...
-        this._log.error("Sync encountered an error", exception);
-        this.resetFileLog();
+        this.resetFileLog(this._logManager.REASON_ERROR);
 
         if (this.shouldReportError()) {
           this.notifyOnNextTick("weave:ui:sync:error");
@@ -644,7 +627,6 @@ ErrorHandler.prototype = {
 
         this.dontIgnoreErrors = false;
         break;
-      }
       case "weave:service:sync:finish":
         this._log.trace("Status.service is " + Status.service);
 
@@ -660,8 +642,8 @@ ErrorHandler.prototype = {
         }
 
         if (Status.service == SYNC_FAILED_PARTIAL) {
-          this._log.error("Some engines did not sync correctly.");
-          this.resetFileLog();
+          this._log.debug("Some engines did not sync correctly.");
+          this.resetFileLog(this._logManager.REASON_ERROR);
 
           if (this.shouldReportError()) {
             this.dontIgnoreErrors = false;
@@ -669,7 +651,7 @@ ErrorHandler.prototype = {
             break;
           }
         } else {
-          this.resetFileLog();
+          this.resetFileLog(this._logManager.REASON_SUCCESS);
         }
         this.dontIgnoreErrors = false;
         this.notifyOnNextTick("weave:ui:sync:finish");
@@ -696,52 +678,22 @@ ErrorHandler.prototype = {
     Utils.nextTick(this.service.sync, this.service);
   },
 
-  _dumpAddons: function _dumpAddons() {
-    // Just dump the items that sync may be concerned with. Specifically,
-    // active extensions that are not hidden.
-    let addonPromise = new Promise(resolve => {
-      try {
-        AddonManager.getAddonsByTypes(["extension"], resolve);
-      } catch (e) {
-        this._log.warn("Failed to dump addons", e)
-        resolve([])
-      }
-    });
-
-    return addonPromise.then(addons => {
-      let relevantAddons = addons.filter(x => x.isActive && !x.hidden);
-      this._log.debug("Addons installed", relevantAddons.length);
-      for (let addon of relevantAddons) {
-        this._log.debug(" - ${name}, version ${version}, id ${id}", addon);
-      }
-    });
-  },
-
   /**
    * Generate a log file for the sync that just completed
    * and refresh the input & output streams.
+   *
+   * @param reason
+   *        A constant from the LogManager that indicates the reason for the
+   *        reset.
    */
-  resetFileLog: function resetFileLog() {
-    let onComplete = logType => {
+  resetFileLog: function resetFileLog(reason) {
+    let onComplete = () => {
       Svc.Obs.notify("weave:service:reset-file-log");
       this._log.trace("Notified: " + Date.now());
-      if (logType == this._logManager.ERROR_LOG_WRITTEN) {
-        Cu.reportError("Sync encountered an error - see about:sync-log for the log file.");
-      }
     };
-
-    // If we're writing an error log, dump extensions that may be causing problems.
-    let beforeResetLog;
-    if (this._logManager.sawError) {
-      beforeResetLog = this._dumpAddons();
-    } else {
-      beforeResetLog = Promise.resolve();
-    }
     // Note we do not return the promise here - the caller doesn't need to wait
     // for this to complete.
-    beforeResetLog
-      .then(() => this._logManager.resetFileLog())
-      .then(onComplete, onComplete);
+    this._logManager.resetFileLog(reason).then(onComplete, onComplete);
   },
 
   /**
@@ -775,9 +727,6 @@ ErrorHandler.prototype = {
     }
   },
 
-  // A function to indicate if Sync errors should be "reported" - which in this
-  // context really means "should be notify observers of an error" - but note
-  // that since bug 1180587, no one is going to surface an error to the user.
   shouldReportError: function shouldReportError() {
     if (Status.login == MASTER_PASSWORD_LOCKED) {
       this._log.trace("shouldReportError: false (master password locked).");
@@ -817,12 +766,8 @@ ErrorHandler.prototype = {
       return false;
     }
 
-
-    let result = ([Status.login, Status.sync].indexOf(SERVER_MAINTENANCE) == -1 &&
-                  [Status.login, Status.sync].indexOf(LOGIN_FAILED_NETWORK_ERROR) == -1);
-    this._log.trace("shouldReportError: ${result} due to login=${login}, sync=${sync}",
-                    {result, login: Status.login, sync: Status.sync});
-    return result;
+    return ([Status.login, Status.sync].indexOf(SERVER_MAINTENANCE) == -1 &&
+            [Status.login, Status.sync].indexOf(LOGIN_FAILED_NETWORK_ERROR) == -1);
   },
 
   get currentAlertMode() {
@@ -925,7 +870,7 @@ ErrorHandler.prototype = {
       case 401:
         this.service.logout();
         this._log.info("Got 401 response; resetting clusterURL.");
-        this.service.clusterURL = null;
+        Svc.Prefs.reset("clusterURL");
 
         let delay = 0;
         if (Svc.Prefs.get("lastSyncReassigned")) {
diff --git a/services/sync/modules/record.js b/services/sync/modules/record.js
index f7a69d9ef..04ccd2dd2 100644
--- a/services/sync/modules/record.js
+++ b/services/sync/modules/record.js
@@ -10,10 +10,10 @@ this.EXPORTED_SYMBOLS = [
   "Collection",
 ];
 
-var Cc = Components.classes;
-var Ci = Components.interfaces;
-var Cr = Components.results;
-var Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+const Cu = Components.utils;
 
 const CRYPTO_COLLECTION = "crypto";
 const KEYS_WBO = "keys";
@@ -23,7 +23,6 @@ Cu.import("resource://services-sync/constants.js");
 Cu.import("resource://services-sync/keys.js");
 Cu.import("resource://services-sync/resource.js");
 Cu.import("resource://services-sync/util.js");
-Cu.import("resource://services-common/async.js");
 
 this.WBORecord = function WBORecord(collection, id) {
   this.data = {};
@@ -86,7 +85,7 @@ WBORecord.prototype = {
   toJSON: function toJSON() {
     // Copy fields from data to be stringified, making sure payload is a string
     let obj = {};
-    for (let [key, val] of Object.entries(this.data))
+    for (let [key, val] in Iterator(this.data))
       obj[key] = key == "payload" ? JSON.stringify(val) : val;
     if (this.ttl)
       obj.ttl = this.ttl;
@@ -196,9 +195,7 @@ CryptoWrapper.prototype = {
   },
 
   // The custom setter below masks the parent's getter, so explicitly call it :(
-  get id() {
-    return WBORecord.prototype.__lookupGetter__("id").call(this);
-  },
+  get id() WBORecord.prototype.__lookupGetter__("id").call(this),
 
   // Keep both plaintext and encrypted versions of the id to verify integrity
   set id(val) {
@@ -238,11 +235,8 @@ RecordManager.prototype = {
       record.deserialize(this.response);
 
       return this.set(url, record);
-    } catch (ex) {
-      if (Async.isShutdownException(ex)) {
-        throw ex;
-      }
-      this._log.debug("Failed to import record", ex);
+    } catch(ex) {
+      this._log.debug("Failed to import record: " + Utils.exceptionStr(ex));
       return null;
     }
   },
@@ -281,10 +275,10 @@ RecordManager.prototype = {
  * You can update this thing simply by giving it /info/collections. It'll
  * use the last modified time to bring itself up to date.
  */
-this.CollectionKeyManager = function CollectionKeyManager(lastModified, default_, collections) {
-  this.lastModified = lastModified || 0;
-  this._default = default_ || null;
-  this._collections = collections || {};
+this.CollectionKeyManager = function CollectionKeyManager() {
+  this.lastModified = 0;
+  this._collections = {};
+  this._default = null;
 
   this._log = Log.repository.getLogger("Sync.CollectionKeyManager");
 }
@@ -293,19 +287,6 @@ this.CollectionKeyManager = function CollectionKeyManager(lastModified, default_
 // Note that the last modified time needs to be preserved.
 CollectionKeyManager.prototype = {
 
-  /**
-   * Generate a new CollectionKeyManager that has the same attributes
-   * as this one.
-   */
-  clone() {
-    const newCollections = {};
-    for (let c in this._collections) {
-      newCollections[c] = this._collections[c];
-    }
-
-    return new CollectionKeyManager(this.lastModified, this._default, newCollections);
-  },
-
   // Return information about old vs new keys:
   // * same: true if two collections are equal
   // * changed: an array of collection names that changed.
@@ -328,7 +309,7 @@ CollectionKeyManager.prototype = {
     // Return a sorted, unique array.
     changed.sort();
     let last;
-    changed = changed.filter(x => (x != last) && (last = x));
+    changed = [x for each (x in changed) if ((x != last) && (last = x))];
     return {same: changed.length == 0,
             changed: changed};
   },
@@ -374,15 +355,15 @@ CollectionKeyManager.prototype = {
   /**
    * Create a WBO for the current keys.
    */
-  asWBO: function(collection, id) {
-    return this._makeWBO(this._collections, this._default);
-  },
+  asWBO: function(collection, id)
+    this._makeWBO(this._collections, this._default),
 
   /**
    * Compute a new default key, and new keys for any specified collections.
    */
   newKeys: function(collections) {
-    let newDefaultKeyBundle = this.newDefaultKeyBundle();
+    let newDefaultKey = new BulkKeyBundle(DEFAULT_KEYBUNDLE_NAME);
+    newDefaultKey.generateRandom();
 
     let newColls = {};
     if (collections) {
@@ -392,7 +373,7 @@ CollectionKeyManager.prototype = {
         newColls[c] = b;
       });
     }
-    return [newDefaultKeyBundle, newColls];
+    return [newDefaultKey, newColls];
   },
 
   /**
@@ -406,57 +387,6 @@ CollectionKeyManager.prototype = {
     return this._makeWBO(newColls, newDefaultKey);
   },
 
-  /**
-   * Create a new default key.
-   *
-   * @returns {BulkKeyBundle}
-   */
-  newDefaultKeyBundle() {
-    const key = new BulkKeyBundle(DEFAULT_KEYBUNDLE_NAME);
-    key.generateRandom();
-    return key;
-  },
-
-  /**
-   * Create a new default key and store it as this._default, since without one you cannot use setContents.
-   */
-  generateDefaultKey() {
-    this._default = this.newDefaultKeyBundle();
-  },
-
-  /**
-   * Return true if keys are already present for each of the given
-   * collections.
-   */
-  hasKeysFor(collections) {
-    // We can't use filter() here because sometimes collections is an iterator.
-    for (let collection of collections) {
-      if (!this._collections[collection]) {
-        return false;
-      }
-    }
-    return true;
-  },
-
-  /**
-   * Return a new CollectionKeyManager that has keys for each of the
-   * given collections (creating new ones for collections where we
-   * don't already have keys).
-   */
-  ensureKeysFor(collections) {
-    const newKeys = Object.assign({}, this._collections);
-    for (let c of collections) {
-      if (newKeys[c]) {
-        continue;  // don't replace existing keys
-      }
-
-      const b = new BulkKeyBundle(c);
-      b.generateRandom();
-      newKeys[c] = b;
-    }
-    return new CollectionKeyManager(this.lastModified, this._default, newKeys);
-  },
-
   // Take the fetched info/collections WBO, checking the change
   // time of the crypto collection.
   updateNeeded: function(info_collections) {
@@ -487,6 +417,9 @@ CollectionKeyManager.prototype = {
   //
   setContents: function setContents(payload, modified) {
 
+    if (!modified)
+      throw "No modified time provided to setContents.";
+
     let self = this;
 
     this._log.info("Setting collection keys contents. Our last modified: " +
@@ -516,7 +449,9 @@ CollectionKeyManager.prototype = {
         if (v) {
           let keyObj = new BulkKeyBundle(k);
           keyObj.keyPairB64 = v;
-          newCollections[k] = keyObj;
+          if (keyObj) {
+            newCollections[k] = keyObj;
+          }
         }
       }
     }
@@ -527,11 +462,8 @@ CollectionKeyManager.prototype = {
     let sameColls = collComparison.same;
 
     if (sameDefault && sameColls) {
-      self._log.info("New keys are the same as our old keys!");
-      if (modified) {
-        self._log.info("Bumped local modified time.");
-        self.lastModified = modified;
-      }
+      self._log.info("New keys are the same as our old keys! Bumped local modified time.");
+      self.lastModified = modified;
       return false;
     }
 
@@ -543,10 +475,8 @@ CollectionKeyManager.prototype = {
     this._collections = newCollections;
 
     // Always trust the server.
-    if (modified) {
-      self._log.info("Bumping last modified to " + modified);
-      self.lastModified = modified;
-    }
+    self._log.info("Bumping last modified to " + modified);
+    self.lastModified = modified;
 
     return sameDefault ? collComparison.changed : true;
   },
@@ -594,12 +524,6 @@ this.Collection = function Collection(uri, recordObj, service) {
   this._older = 0;
   this._newer = 0;
   this._data = [];
-  // optional members used by batch upload operations.
-  this._batch = null;
-  this._commit = false;
-  // Used for batch download operations -- note that this is explicitly an
-  // opaque value and not (necessarily) a number.
-  this._offset = null;
 }
 Collection.prototype = {
   __proto__: Resource.prototype,
@@ -623,12 +547,6 @@ Collection.prototype = {
       args.push("ids=" + this.ids);
     if (this.limit > 0 && this.limit != Infinity)
       args.push("limit=" + this.limit);
-    if (this._batch)
-      args.push("batch=" + encodeURIComponent(this._batch));
-    if (this._commit)
-      args.push("commit=true");
-    if (this._offset)
-      args.push("offset=" + encodeURIComponent(this._offset));
 
     this.uri.query = (args.length > 0)? '?' + args.join('&') : '';
   },
@@ -641,14 +559,14 @@ Collection.prototype = {
   },
 
   // Apply the action to a certain set of ids
-  get ids() { return this._ids; },
+  get ids() this._ids,
   set ids(value) {
     this._ids = value;
     this._rebuildURL();
   },
 
   // Limit how many records to get
-  get limit() { return this._limit; },
+  get limit() this._limit,
   set limit(value) {
     this._limit = value;
     this._rebuildURL();
@@ -678,100 +596,12 @@ Collection.prototype = {
     this._rebuildURL();
   },
 
-  get offset() { return this._offset; },
-  set offset(value) {
-    this._offset = value;
-    this._rebuildURL();
-  },
-
-  // Set information about the batch for this request.
-  get batch() { return this._batch; },
-  set batch(value) {
-    this._batch = value;
-    this._rebuildURL();
-  },
-
-  get commit() { return this._commit; },
-  set commit(value) {
-    this._commit = value && true;
-    this._rebuildURL();
+  pushData: function Coll_pushData(data) {
+    this._data.push(data);
   },
 
-  // Similar to get(), but will page through the items `batchSize` at a time,
-  // deferring calling the record handler until we've gotten them all.
-  //
-  // Returns the last response processed, and doesn't run the record handler
-  // on any items if a non-success status is received while downloading the
-  // records (or if a network error occurs).
-  getBatched(batchSize = DEFAULT_DOWNLOAD_BATCH_SIZE) {
-    let totalLimit = Number(this.limit) || Infinity;
-    if (batchSize <= 0 || batchSize >= totalLimit) {
-      // Invalid batch sizes should arguably be an error, but they're easy to handle
-      return this.get();
-    }
-
-    if (!this.full) {
-      throw new Error("getBatched is unimplemented for guid-only GETs");
-    }
-
-    // _onComplete and _onProgress are reset after each `get` by AsyncResource.
-    // We overwrite _onRecord to something that stores the data in an array
-    // until the end.
-    let { _onComplete, _onProgress, _onRecord } = this;
-    let recordBuffer = [];
-    let resp;
-    try {
-      this._onRecord = r => recordBuffer.push(r);
-      let lastModifiedTime;
-      this.limit = batchSize;
-
-      do {
-        this._onProgress = _onProgress;
-        this._onComplete = _onComplete;
-        if (batchSize + recordBuffer.length > totalLimit) {
-          this.limit = totalLimit - recordBuffer.length;
-        }
-        this._log.trace("Performing batched GET", { limit: this.limit, offset: this.offset });
-        // Actually perform the request
-        resp = this.get();
-        if (!resp.success) {
-          break;
-        }
-
-        // Initialize last modified, or check that something broken isn't happening.
-        let lastModified = resp.headers["x-last-modified"];
-        if (!lastModifiedTime) {
-          lastModifiedTime = lastModified;
-          this.setHeader("X-If-Unmodified-Since", lastModified);
-        } else if (lastModified != lastModifiedTime) {
-          // Should be impossible -- We'd get a 412 in this case.
-          throw new Error("X-Last-Modified changed in the middle of a download batch! " +
-                          `${lastModified} => ${lastModifiedTime}`)
-        }
-
-        // If this is missing, we're finished.
-        this.offset = resp.headers["x-weave-next-offset"];
-      } while (this.offset && totalLimit > recordBuffer.length);
-    } finally {
-      // Ensure we undo any temporary state so that subsequent calls to get()
-      // or getBatched() work properly. We do this before calling the record
-      // handler so that we can more convincingly pretend to be a normal get()
-      // call. Note: we're resetting these to the values they had before this
-      // function was called.
-      this._onRecord = _onRecord;
-      this._limit = totalLimit;
-      this._offset = null;
-      delete this._headers["x-if-unmodified-since"];
-      this._rebuildURL();
-    }
-    if (resp.success && Async.checkAppReady()) {
-      // call the original _onRecord (e.g. the user supplied record handler)
-      // for each record we've stored
-      for (let record of recordBuffer) {
-        this._onRecord(record);
-      }
-    }
-    return resp;
+  clearRecords: function Coll_clearRecords() {
+    this._data = [];
   },
 
   set recordHandler(onRecord) {
@@ -781,8 +611,6 @@ Collection.prototype = {
     // Switch to newline separated records for incremental parsing
     coll.setHeader("Accept", "application/newlines");
 
-    this._onRecord = onRecord;
-
     this._onProgress = function() {
       let newline;
       while ((newline = this._data.indexOf("\n")) > 0) {
@@ -793,247 +621,8 @@ Collection.prototype = {
         // Deserialize a record from json and give it to the callback
         let record = new coll._recordObj();
         record.deserialize(json);
-        coll._onRecord(record);
+        onRecord(record);
       }
     };
   },
-
-  // This object only supports posting via the postQueue object.
-  post() {
-    throw new Error("Don't directly post to a collection - use newPostQueue instead");
-  },
-
-  newPostQueue(log, timestamp, postCallback) {
-    let poster = (data, headers, batch, commit) => {
-      this.batch = batch;
-      this.commit = commit;
-      for (let [header, value] of headers) {
-        this.setHeader(header, value);
-      }
-      return Resource.prototype.post.call(this, data);
-    }
-    let getConfig = (name, defaultVal) => {
-      if (this._service.serverConfiguration && this._service.serverConfiguration.hasOwnProperty(name)) {
-        return this._service.serverConfiguration[name];
-      }
-      return defaultVal;
-    }
-
-    let config = {
-      max_post_bytes: getConfig("max_post_bytes", MAX_UPLOAD_BYTES),
-      max_post_records: getConfig("max_post_records", MAX_UPLOAD_RECORDS),
-
-      max_batch_bytes: getConfig("max_total_bytes", Infinity),
-      max_batch_records: getConfig("max_total_records", Infinity),
-    }
-
-    // Handle config edge cases
-    if (config.max_post_records <= 0) { config.max_post_records = MAX_UPLOAD_RECORDS; }
-    if (config.max_batch_records <= 0) { config.max_batch_records = Infinity; }
-    if (config.max_post_bytes <= 0) { config.max_post_bytes = MAX_UPLOAD_BYTES; }
-    if (config.max_batch_bytes <= 0) { config.max_batch_bytes = Infinity; }
-
-    // Max size of BSO payload is 256k. This assumes at most 4k of overhead,
-    // which sounds like plenty. If the server says it can't handle this, we
-    // might have valid records we can't sync, so we give up on syncing.
-    let requiredMax = 260 * 1024;
-    if (config.max_post_bytes < requiredMax) {
-      this._log.error("Server configuration max_post_bytes is too low", config);
-      throw new Error("Server configuration max_post_bytes is too low");
-    }
-
-    return new PostQueue(poster, timestamp, config, log, postCallback);
-  },
 };
-
-/* A helper to manage the posting of records while respecting the various
-   size limits.
-
-   This supports the concept of a server-side "batch". The general idea is:
-   * We queue as many records as allowed in memory, then make a single POST.
-   * This first POST (optionally) gives us a batch ID, which we use for
-     all subsequent posts, until...
-   * At some point we hit a batch-maximum, and jump through a few hoops to
-     commit the current batch (ie, all previous POSTs) and start a new one.
-   * Eventually commit the final batch.
-
-  In most cases we expect there to be exactly 1 batch consisting of possibly
-  multiple POSTs.
-*/
-function PostQueue(poster, timestamp, config, log, postCallback) {
-  // The "post" function we should use when it comes time to do the post.
-  this.poster = poster;
-  this.log = log;
-
-  // The config we use. We expect it to have fields "max_post_records",
-  // "max_batch_records", "max_post_bytes", and "max_batch_bytes"
-  this.config = config;
-
-  // The callback we make with the response when we do get around to making the
-  // post (which could be during any of the enqueue() calls or the final flush())
-  // This callback may be called multiple times and must not add new items to
-  // the queue.
-  // The second argument passed to this callback is a boolean value that is true
-  // if we're in the middle of a batch, and false if either the batch is
-  // complete, or it's a post to a server that does not understand batching.
-  this.postCallback = postCallback;
-
-  // The string where we are capturing the stringified version of the records
-  // queued so far. It will always be invalid JSON as it is always missing the
-  // closing bracket.
-  this.queued = "";
-
-  // The number of records we've queued so far but are yet to POST.
-  this.numQueued = 0;
-
-  // The number of records/bytes we've processed in previous POSTs for our
-  // current batch. Does *not* include records currently queued for the next POST.
-  this.numAlreadyBatched = 0;
-  this.bytesAlreadyBatched = 0;
-
-  // The ID of our current batch. Can be undefined (meaning we are yet to make
-  // the first post of a patch, so don't know if we have a batch), null (meaning
-  // we've made the first post but the server response indicated no batching
-  // semantics), otherwise we have made the first post and it holds the batch ID
-  // returned from the server.
-  this.batchID = undefined;
-
-  // Time used for X-If-Unmodified-Since -- should be the timestamp from the last GET.
-  this.lastModified = timestamp;
-}
-
-PostQueue.prototype = {
-  enqueue(record) {
-    // We want to ensure the record has a .toJSON() method defined - even
-    // though JSON.stringify() would implicitly call it, the stringify might
-    // still work even if it isn't defined, which isn't what we want.
-    let jsonRepr = record.toJSON();
-    if (!jsonRepr) {
-      throw new Error("You must only call this with objects that explicitly support JSON");
-    }
-    let bytes = JSON.stringify(jsonRepr);
-
-    // Do a flush if we can't add this record without exceeding our single-request
-    // limits, or without exceeding the total limit for a single batch.
-    let newLength = this.queued.length + bytes.length + 2; // extras for leading "[" / "," and trailing "]"
-
-    let maxAllowedBytes = Math.min(256 * 1024, this.config.max_post_bytes);
-
-    let postSizeExceeded = this.numQueued >= this.config.max_post_records ||
-                           newLength >= maxAllowedBytes;
-
-    let batchSizeExceeded = (this.numQueued + this.numAlreadyBatched) >= this.config.max_batch_records ||
-                            (newLength + this.bytesAlreadyBatched) >= this.config.max_batch_bytes;
-
-    let singleRecordTooBig = bytes.length + 2 > maxAllowedBytes;
-
-    if (postSizeExceeded || batchSizeExceeded) {
-      this.log.trace(`PostQueue flushing due to postSizeExceeded=${postSizeExceeded}, batchSizeExceeded=${batchSizeExceeded}` +
-                     `, max_batch_bytes: ${this.config.max_batch_bytes}, max_post_bytes: ${this.config.max_post_bytes}`);
-
-      if (singleRecordTooBig) {
-        return { enqueued: false, error: new Error("Single record too large to submit to server") };
-      }
-
-      // We need to write the queue out before handling this one, but we only
-      // commit the batch (and thus start a new one) if the batch is full.
-      // Note that if a single record is too big for the batch or post, then
-      // the batch may be empty, and so we don't flush in that case.
-      if (this.numQueued) {
-        this.flush(batchSizeExceeded || singleRecordTooBig);
-      }
-    }
-    // Either a ',' or a '[' depending on whether this is the first record.
-    this.queued += this.numQueued ? "," : "[";
-    this.queued += bytes;
-    this.numQueued++;
-    return { enqueued: true };
-  },
-
-  flush(finalBatchPost) {
-    if (!this.queued) {
-      // nothing queued - we can't be in a batch, and something has gone very
-      // bad if we think we are.
-      if (this.batchID) {
-        throw new Error(`Flush called when no queued records but we are in a batch ${this.batchID}`);
-      }
-      return;
-    }
-    // the batch query-param and headers we'll send.
-    let batch;
-    let headers = [];
-    if (this.batchID === undefined) {
-      // First commit in a (possible) batch.
-      batch = "true";
-    } else if (this.batchID) {
-      // We have an existing batch.
-      batch = this.batchID;
-    } else {
-      // Not the first post and we know we have no batch semantics.
-      batch = null;
-    }
-
-    headers.push(["x-if-unmodified-since", this.lastModified]);
-
-    this.log.info(`Posting ${this.numQueued} records of ${this.queued.length+1} bytes with batch=${batch}`);
-    let queued = this.queued + "]";
-    if (finalBatchPost) {
-      this.bytesAlreadyBatched = 0;
-      this.numAlreadyBatched = 0;
-    } else {
-      this.bytesAlreadyBatched += queued.length;
-      this.numAlreadyBatched += this.numQueued;
-    }
-    this.queued = "";
-    this.numQueued = 0;
-    let response = this.poster(queued, headers, batch, !!(finalBatchPost && this.batchID !== null));
-
-    if (!response.success) {
-      this.log.trace("Server error response during a batch", response);
-      // not clear what we should do here - we expect the consumer of this to
-      // abort by throwing in the postCallback below.
-      return this.postCallback(response, !finalBatchPost);
-    }
-
-    if (finalBatchPost) {
-      this.log.trace("Committed batch", this.batchID);
-      this.batchID = undefined; // we are now in "first post for the batch" state.
-      this.lastModified = response.headers["x-last-modified"];
-      return this.postCallback(response, false);
-    }
-
-    if (response.status != 202) {
-      if (this.batchID) {
-        throw new Error("Server responded non-202 success code while a batch was in progress");
-      }
-      this.batchID = null; // no batch semantics are in place.
-      this.lastModified = response.headers["x-last-modified"];
-      return this.postCallback(response, false);
-    }
-
-    // this response is saying the server has batch semantics - we should
-    // always have a batch ID in the response.
-    let responseBatchID = response.obj.batch;
-    this.log.trace("Server responsed 202 with batch", responseBatchID);
-    if (!responseBatchID) {
-      this.log.error("Invalid server response: 202 without a batch ID", response);
-      throw new Error("Invalid server response: 202 without a batch ID");
-    }
-
-    if (this.batchID === undefined) {
-      this.batchID = responseBatchID;
-      if (!this.lastModified) {
-        this.lastModified = response.headers["x-last-modified"];
-        if (!this.lastModified) {
-          throw new Error("Batch response without x-last-modified");
-        }
-      }
-    }
-
-    if (this.batchID != responseBatchID) {
-      throw new Error(`Invalid client/server batch state - client has ${this.batchID}, server has ${responseBatchID}`);
-    }
-
-    this.postCallback(response, true);
-  },
-}
diff --git a/services/sync/modules/resource.js b/services/sync/modules/resource.js
index bf7066b9f..1c2a67b90 100644
--- a/services/sync/modules/resource.js
+++ b/services/sync/modules/resource.js
@@ -7,13 +7,12 @@ this.EXPORTED_SYMBOLS = [
   "Resource"
 ];
 
-var Cc = Components.classes;
-var Ci = Components.interfaces;
-var Cr = Components.results;
-var Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+const Cu = Components.utils;
 
 Cu.import("resource://gre/modules/Preferences.jsm");
-Cu.import("resource://gre/modules/NetUtil.jsm");
 Cu.import("resource://services-common/async.js");
 Cu.import("resource://gre/modules/Log.jsm");
 Cu.import("resource://services-common/observers.js");
@@ -74,6 +73,20 @@ AsyncResource.prototype = {
    */
   authenticator: null,
 
+  // The string to use as the base User-Agent in Sync requests.
+  // These strings will look something like
+  //
+  //   Firefox/4.0 FxSync/1.8.0.20100101.mobile
+  //
+  // or
+  //
+  //   Firefox Aurora/5.0a1 FxSync/1.9.0.20110409.desktop
+  //
+  _userAgent:
+    Services.appinfo.name + "/" + Services.appinfo.version +  // Product.
+    " FxSync/" + WEAVE_VERSION + "." +                        // Sync.
+    Services.appinfo.appBuildID + ".",                        // Build.
+
   // Wait 5 minutes before killing a request.
   ABORT_TIMEOUT: 300000,
 
@@ -121,9 +134,7 @@ AsyncResource.prototype = {
   //
   // Get and set the data encapulated in the resource.
   _data: null,
-  get data() {
-    return this._data;
-  },
+  get data() this._data,
   set data(value) {
     this._data = value;
   },
@@ -135,9 +146,16 @@ AsyncResource.prototype = {
   // to obtain a request channel.
   //
   _createRequest: function Res__createRequest(method) {
-    let channel = NetUtil.newChannel({uri: this.spec, loadUsingSystemPrincipal: true})
-                         .QueryInterface(Ci.nsIRequest)
-                         .QueryInterface(Ci.nsIHttpChannel);
+    let channel = Services.io.newChannel2(this.spec,
+                                          null,
+                                          null,
+                                          null,      // aLoadingNode
+                                          Services.scriptSecurityManager.getSystemPrincipal(),
+                                          null,      // aTriggeringPrincipal
+                                          Ci.nsILoadInfo.SEC_NORMAL,
+                                          Ci.nsIContentPolicy.TYPE_OTHER)
+                          .QueryInterface(Ci.nsIRequest)
+                          .QueryInterface(Ci.nsIHttpChannel);
 
     channel.loadFlags |= DEFAULT_LOAD_FLAGS;
 
@@ -147,7 +165,8 @@ AsyncResource.prototype = {
 
     // Compose a UA string fragment from the various available identifiers.
     if (Svc.Prefs.get("sendVersionInfo", true)) {
-      channel.setRequestHeader("user-agent", Utils.userAgent, false);
+      let ua = this._userAgent + Svc.Prefs.get("client.type", "desktop");
+      channel.setRequestHeader("user-agent", ua, false);
     }
 
     let headers = this.headers;
@@ -155,7 +174,7 @@ AsyncResource.prototype = {
     if (this.authenticator) {
       let result = this.authenticator(this, method);
       if (result && result.headers) {
-        for (let [k, v] of Object.entries(result.headers)) {
+        for (let [k, v] in Iterator(result.headers)) {
           headers[k.toLowerCase()] = v;
         }
       }
@@ -163,7 +182,7 @@ AsyncResource.prototype = {
       this._log.debug("No authenticator found.");
     }
 
-    for (let [key, value] of Object.entries(headers)) {
+    for (let [key, value] in Iterator(headers)) {
       if (key == 'authorization')
         this._log.trace("HTTP Header " + key + ": ***** (suppressed)");
       else
@@ -209,10 +228,10 @@ AsyncResource.prototype = {
                                        this._log, this.ABORT_TIMEOUT);
     channel.requestMethod = action;
     try {
-      channel.asyncOpen2(listener);
+      channel.asyncOpen(listener, null);
     } catch (ex) {
-      // asyncOpen2 can throw in a bunch of cases -- e.g., a forbidden port.
-      this._log.warn("Caught an error in asyncOpen2", ex);
+      // asyncOpen can throw in a bunch of cases -- e.g., a forbidden port.
+      this._log.warn("Caught an error in asyncOpen: " + CommonUtils.exceptionStr(ex));
       CommonUtils.nextTick(callback.bind(this, ex));
     }
   },
@@ -259,7 +278,9 @@ AsyncResource.prototype = {
     } catch(ex) {
       // Got a response, but an exception occurred during processing.
       // This shouldn't occur.
-      this._log.warn("Caught unexpected exception in _oncomplete", ex);
+      this._log.warn("Caught unexpected exception " + CommonUtils.exceptionStr(ex) +
+                     " in _onComplete.");
+      this._log.debug(CommonUtils.stackTrace(ex));
     }
 
     // Process headers. They can be empty, or the call can otherwise fail, so
@@ -297,18 +318,16 @@ AsyncResource.prototype = {
                        contentLength + ".");
       }
     } catch (ex) {
-      this._log.debug("Caught exception visiting headers in _onComplete", ex);
+      this._log.debug("Caught exception " + CommonUtils.exceptionStr(ex) +
+                      " visiting headers in _onComplete.");
+      this._log.debug(CommonUtils.stackTrace(ex));
     }
 
     let ret     = new String(data);
-    ret.url     = channel.URI.spec;
     ret.status  = status;
     ret.success = success;
     ret.headers = headers;
 
-    if (!success) {
-      this._log.warn(`${action} request to ${ret.url} failed with status ${status}`);
-    }
     // Make a lazy getter to convert the json response into an object.
     // Note that this can cause a parse error to be thrown far away from the
     // actual fetch, so be warned!
@@ -316,7 +335,7 @@ AsyncResource.prototype = {
       try {
         return JSON.parse(ret);
       } catch (ex) {
-        this._log.warn("Got exception parsing response body", ex);
+        this._log.warn("Got exception parsing response body: \"" + CommonUtils.exceptionStr(ex));
         // Stringify to avoid possibly printing non-printable characters.
         this._log.debug("Parse fail: Response body starts: \"" +
                         JSON.stringify((ret + "").slice(0, 100)) +
@@ -384,12 +403,7 @@ Resource.prototype = {
     try {
       this._doRequest(action, data, callback);
       return Async.waitForSyncCallback(cb);
-    } catch (ex) {
-      if (Async.isShutdownException(ex)) {
-        throw ex;
-      }
-      this._log.warn("${action} request to ${url} failed: ${ex}",
-                     { action, url: this.uri.spec, ex });
+    } catch(ex) {
       // Combine the channel stack with this request stack.  Need to create
       // a new error object for that.
       let error = Error(ex.message);
@@ -527,7 +541,7 @@ ChannelListener.prototype = {
       siStream = Cc["@mozilla.org/scriptableinputstream;1"].createInstance(Ci.nsIScriptableInputStream);
       siStream.init(stream);
     } catch (ex) {
-      this._log.warn("Exception creating nsIScriptableInputStream", ex);
+      this._log.warn("Exception creating nsIScriptableInputStream." + CommonUtils.exceptionStr(ex));
       this._log.debug("Parameters: " + req.URI.spec + ", " + stream + ", " + off + ", " + count);
       // Cannot proceed, so rethrow and allow the channel to cancel itself.
       throw ex;
@@ -543,11 +557,9 @@ ChannelListener.prototype = {
     try {
       this._onProgress();
     } catch (ex) {
-      if (Async.isShutdownException(ex)) {
-        throw ex;
-      }
       this._log.warn("Got exception calling onProgress handler during fetch of "
-                     + req.URI.spec, ex);
+                     + req.URI.spec);
+      this._log.debug(CommonUtils.exceptionStr(ex));
       this._log.trace("Rethrowing; expect a failure code from the HTTP channel.");
       throw ex;
     }
@@ -562,7 +574,7 @@ ChannelListener.prototype = {
     try {
       CommonUtils.namedTimer(this.abortRequest, this._timeout, this, "abortTimer");
     } catch (ex) {
-      this._log.warn("Got exception extending abort timer", ex);
+      this._log.warn("Got exception extending abort timer: " + CommonUtils.exceptionStr(ex));
     }
   },
 
@@ -656,14 +668,14 @@ ChannelNotificationListener.prototype = {
         }
       }
     } catch (ex) {
-      this._log.error("Error copying headers", ex);
+      this._log.error("Error copying headers: " + CommonUtils.exceptionStr(ex));
     }
 
     // We let all redirects proceed.
     try {
       callback.onRedirectVerifyCallback(Cr.NS_OK);
     } catch (ex) {
-      this._log.error("onRedirectVerifyCallback threw!", ex);
+      this._log.error("onRedirectVerifyCallback threw!" + CommonUtils.exceptionStr(ex));
     }
   }
 };
diff --git a/services/sync/modules/rest.js b/services/sync/modules/rest.js
index 94c096dba..34382eed5 100644
--- a/services/sync/modules/rest.js
+++ b/services/sync/modules/rest.js
@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-var {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
 
 Cu.import("resource://gre/modules/Log.jsm");
 Cu.import("resource://services-common/rest.js");
@@ -28,6 +28,21 @@ SyncStorageRequest.prototype = {
   _logName: "Sync.StorageRequest",
 
   /**
+   * The string to use as the base User-Agent in Sync requests.
+   * These strings will look something like
+   * 
+   *   Firefox/4.0 FxSync/1.8.0.20100101.mobile
+   * 
+   * or
+   * 
+   *   Firefox Aurora/5.0a1 FxSync/1.9.0.20110409.desktop
+   */
+  userAgent:
+    Services.appinfo.name + "/" + Services.appinfo.version +  // Product.
+    " FxSync/" + WEAVE_VERSION + "." +                        // Sync.
+    Services.appinfo.appBuildID + ".",                        // Build.
+
+  /**
    * Wait 5 minutes before killing a request.
    */
   timeout: STORAGE_REQUEST_TIMEOUT,
@@ -35,7 +50,8 @@ SyncStorageRequest.prototype = {
   dispatch: function dispatch(method, data, onComplete, onProgress) {
     // Compose a UA string fragment from the various available identifiers.
     if (Svc.Prefs.get("sendVersionInfo", true)) {
-      this.setHeader("user-agent", Utils.userAgent);
+      let ua = this.userAgent + Svc.Prefs.get("client.type", "desktop");
+      this.setHeader("user-agent", ua);
     }
 
     if (this.authenticator) {
diff --git a/services/sync/modules/service.js b/services/sync/modules/service.js
index 32e047f53..637760b8f 100644
--- a/services/sync/modules/service.js
+++ b/services/sync/modules/service.js
@@ -4,10 +4,10 @@
 
 this.EXPORTED_SYMBOLS = ["Service"];
 
-var Cc = Components.classes;
-var Ci = Components.interfaces;
-var Cr = Components.results;
-var Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+const Cu = Components.utils;
 
 // How long before refreshing the cluster
 const CLUSTER_BACKOFF = 5 * 60 * 1000; // 5 minutes
@@ -21,6 +21,7 @@ const KEYS_WBO = "keys";
 Cu.import("resource://gre/modules/Preferences.jsm");
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Log.jsm");
+Cu.import("resource://services-common/utils.js");
 Cu.import("resource://services-sync/constants.js");
 Cu.import("resource://services-sync/engines.js");
 Cu.import("resource://services-sync/engines/clients.js");
@@ -32,7 +33,6 @@ Cu.import("resource://services-sync/rest.js");
 Cu.import("resource://services-sync/stages/enginesync.js");
 Cu.import("resource://services-sync/stages/declined.js");
 Cu.import("resource://services-sync/status.js");
-Cu.import("resource://services-sync/telemetry.js");
 Cu.import("resource://services-sync/userapi.js");
 Cu.import("resource://services-sync/util.js");
 
@@ -51,6 +51,15 @@ const STORAGE_INFO_TYPES = [INFO_COLLECTIONS,
                             INFO_COLLECTION_COUNTS,
                             INFO_QUOTA];
 
+// A structure mapping a (boolean) telemetry probe name to a preference name.
+// The probe will record true if the pref is modified, false otherwise.
+const TELEMETRY_CUSTOM_SERVER_PREFS = {
+  WEAVE_CUSTOM_LEGACY_SERVER_CONFIGURATION: "services.sync.serverURL",
+  WEAVE_CUSTOM_FXA_SERVER_CONFIGURATION: "identity.fxaccounts.auth.uri",
+  WEAVE_CUSTOM_TOKEN_SERVER_CONFIGURATION: "services.sync.tokenServerURI",
+};
+
+
 function Sync11Service() {
   this._notify = Utils.notify("weave:service:");
 }
@@ -64,13 +73,8 @@ Sync11Service.prototype = {
   storageURL: null,
   metaURL: null,
   cryptoKeyURL: null,
-  // The cluster URL comes via the ClusterManager object, which in the FxA
-  // world is ebbedded in the token returned from the token server.
-  _clusterURL: null,
 
-  get serverURL() {
-    return Svc.Prefs.get("serverURL");
-  },
+  get serverURL() Svc.Prefs.get("serverURL"),
   set serverURL(value) {
     if (!value.endsWith("/")) {
       value += "/";
@@ -80,20 +84,14 @@ Sync11Service.prototype = {
     if (value == this.serverURL)
       return;
 
+    // A new server most likely uses a different cluster, so clear that
     Svc.Prefs.set("serverURL", value);
-
-    // A new server most likely uses a different cluster, so clear that.
-    this._clusterURL = null;
+    Svc.Prefs.reset("clusterURL");
   },
 
-  get clusterURL() {
-    return this._clusterURL || "";
-  },
+  get clusterURL() Svc.Prefs.get("clusterURL", ""),
   set clusterURL(value) {
-    if (value != null && typeof value != "string") {
-      throw new Error("cluster must be a string, got " + (typeof value));
-    }
-    this._clusterURL = value;
+    Svc.Prefs.set("clusterURL", value);
     this._updateCachedURLs();
   },
 
@@ -171,16 +169,8 @@ Sync11Service.prototype = {
 
   _updateCachedURLs: function _updateCachedURLs() {
     // Nothing to cache yet if we don't have the building blocks
-    if (!this.clusterURL || !this.identity.username) {
-      // Also reset all other URLs used by Sync to ensure we aren't accidentally
-      // using one cached earlier - if there's no cluster URL any cached ones
-      // are invalid.
-      this.infoURL = undefined;
-      this.storageURL = undefined;
-      this.metaURL = undefined;
-      this.cryptoKeysURL = undefined;
+    if (!this.clusterURL || !this.identity.username)
       return;
-    }
 
     this._log.debug("Caching URLs under storage user base: " + this.userBaseURL);
 
@@ -315,6 +305,21 @@ Sync11Service.prototype = {
     return false;
   },
 
+  // The global "enabled" state comes from prefs, and will be set to false
+  // whenever the UI that exposes what to sync finds all Sync engines disabled.
+  get enabled() {
+    return Svc.Prefs.get("enabled");
+  },
+  set enabled(val) {
+    // There's no real reason to impose this other than to catch someone doing
+    // something we don't expect with bad consequences - all setting of this
+    // pref are in the UI code and external to this module.
+    if (val) {
+      throw new Error("Only disabling via this setter is supported");
+    }
+    Svc.Prefs.set("enabled", val);
+  },
+
   /**
    * Prepare to initialize the rest of Weave after waiting a little bit
    */
@@ -344,8 +349,6 @@ Sync11Service.prototype = {
     this._clusterManager = this.identity.createClusterManager(this);
     this.recordManager = new RecordManager(this);
 
-    this.enabled = true;
-
     this._registerEngines();
 
     let ua = Cc["@mozilla.org/network/protocol;1?name=http"].
@@ -359,7 +362,6 @@ Sync11Service.prototype = {
     }
 
     Svc.Obs.add("weave:service:setup-complete", this);
-    Svc.Obs.add("sync:collection_changed", this); // Pulled from FxAccountsCommon
     Svc.Prefs.observe("engine.", this);
 
     this.scheduler = new SyncScheduler(this);
@@ -375,6 +377,12 @@ Sync11Service.prototype = {
       Svc.Obs.notify("weave:engine:start-tracking");
     }
 
+    // Telemetry probes to indicate if the user is using custom servers.
+    for (let [probeName, prefName] of Iterator(TELEMETRY_CUSTOM_SERVER_PREFS)) {
+      let isCustomized = Services.prefs.prefHasUserValue(prefName);
+      Services.telemetry.getHistogramById(probeName).add(isCustomized);
+    }
+
     // Send an event now that Weave service is ready.  We don't do this
     // synchronously so that observers can import this module before
     // registering an observer.
@@ -424,7 +432,7 @@ Sync11Service.prototype = {
 
     // Map each old pref to the current pref branch
     let oldPref = new Preferences(oldPrefBranch);
-    for (let pref of oldPrefNames)
+    for each (let pref in oldPrefNames)
       Svc.Prefs.set(pref, oldPref.get(pref));
 
     // Remove all the old prefs and remember that we've migrated
@@ -472,7 +480,8 @@ Sync11Service.prototype = {
 
         this.engineManager.register(ns[engineName]);
       } catch (ex) {
-        this._log.warn("Could not register engine " + name, ex);
+        this._log.warn("Could not register engine " + name + ": " +
+                       CommonUtils.exceptionStr(ex));
       }
     }
 
@@ -486,13 +495,6 @@ Sync11Service.prototype = {
 
   observe: function observe(subject, topic, data) {
     switch (topic) {
-      // Ideally this observer should be in the SyncScheduler, but it would require
-      // some work to know about the sync specific engines. We should move this there once it does.
-      case "sync:collection_changed":
-        if (data.includes("clients")) {
-          this.sync([]); // [] = clients collection only
-        }
-        break;
       case "weave:service:setup-complete":
         let status = this._checkSetup();
         if (status != STATUS_DISABLED && status != CLIENT_NOT_CONFIGURED)
@@ -557,8 +559,7 @@ Sync11Service.prototype = {
     // Always check for errors; this is also where we look for X-Weave-Alert.
     this.errorHandler.checkServerError(info);
     if (!info.success) {
-      this._log.error("Aborting sync: failed to get collections.")
-      throw info;
+      throw "Aborting sync: failed to get collections.";
     }
     return info;
   },
@@ -675,13 +676,21 @@ Sync11Service.prototype = {
 
     } catch (ex) {
       // This means no keys are present, or there's a network error.
-      this._log.debug("Failed to fetch and verify keys", ex);
+      this._log.debug("Failed to fetch and verify keys: "
+                      + Utils.exceptionStr(ex));
       this.errorHandler.checkServerError(ex);
       return false;
     }
   },
 
   verifyLogin: function verifyLogin(allow40XRecovery = true) {
+    // If the identity isn't ready it  might not know the username...
+    if (!this.identity.readyToAuthenticate) {
+      this._log.info("Not ready to authenticate in verifyLogin.");
+      this.status.login = LOGIN_FAILED_NOT_READY;
+      return false;
+    }
+
     if (!this.identity.username) {
       this._log.warn("No username in verifyLogin.");
       this.status.login = LOGIN_FAILED_NO_USERNAME;
@@ -753,12 +762,8 @@ Sync11Service.prototype = {
             return this.verifyLogin(false);
           }
 
-          // We must have the right cluster, but the server doesn't expect us.
-          // The implications of this depend on the identity being used - for
-          // the legacy identity, it's an authoritatively "incorrect password",
-          // (ie, LOGIN_FAILED_LOGIN_REJECTED) but for FxA it probably means
-          // "transient error fetching auth token".
-          this.status.login = this.identity.loginStatusFromVerification404();
+          // We must have the right cluster, but the server doesn't expect us
+          this.status.login = LOGIN_FAILED_LOGIN_REJECTED;
           return false;
 
         default:
@@ -769,7 +774,7 @@ Sync11Service.prototype = {
       }
     } catch (ex) {
       // Must have failed on some network issue
-      this._log.debug("verifyLogin failed", ex);
+      this._log.debug("verifyLogin failed: " + Utils.exceptionStr(ex));
       this.status.login = LOGIN_FAILED_NETWORK_ERROR;
       this.errorHandler.checkServerError(ex);
       return false;
@@ -842,7 +847,8 @@ Sync11Service.prototype = {
     try {
       cb.wait();
     } catch (ex) {
-      this._log.debug("Password change failed", ex);
+      this._log.debug("Password change failed: " +
+                      CommonUtils.exceptionStr(ex));
       return false;
     }
 
@@ -884,11 +890,12 @@ Sync11Service.prototype = {
     // Deletion doesn't make sense if we aren't set up yet!
     if (this.clusterURL != "") {
       // Clear client-specific data from the server, including disabled engines.
-      for (let engine of [this.clientsEngine].concat(this.engineManager.getAll())) {
+      for each (let engine in [this.clientsEngine].concat(this.engineManager.getAll())) {
         try {
           engine.removeClientData();
         } catch(ex) {
-          this._log.warn(`Deleting client data for ${engine.name} failed`, ex);
+          this._log.warn("Deleting client data for " + engine.name + " failed:"
+                         + Utils.exceptionStr(ex));
         }
       }
       this._log.debug("Finished deleting client data.");
@@ -914,7 +921,6 @@ Sync11Service.prototype = {
     this._ignorePrefObserver = true;
     Svc.Prefs.resetBranch("");
     this._ignorePrefObserver = false;
-    this.clusterURL = null;
 
     Svc.Prefs.set("lastversion", WEAVE_VERSION);
 
@@ -931,22 +937,25 @@ Sync11Service.prototype = {
       return;
     }
 
-    try {
-      this.identity.finalize();
-      // an observer so the FxA migration code can take some action before
-      // the new identity is created.
-      Svc.Obs.notify("weave:service:start-over:init-identity");
-      this.identity.username = "";
-      this.status.__authManager = null;
-      this.identity = Status._authManager;
-      this._clusterManager = this.identity.createClusterManager(this);
-      Svc.Obs.notify("weave:service:start-over:finish");
-    } catch (err) {
-      this._log.error("startOver failed to re-initialize the identity manager: " + err);
-      // Still send the observer notification so the current state is
-      // reflected in the UI.
-      Svc.Obs.notify("weave:service:start-over:finish");
-    }
+    this.identity.finalize().then(
+      () => {
+        // an observer so the FxA migration code can take some action before
+        // the new identity is created.
+        Svc.Obs.notify("weave:service:start-over:init-identity");
+        this.identity.username = "";
+        this.status.__authManager = null;
+        this.identity = Status._authManager;
+        this._clusterManager = this.identity.createClusterManager(this);
+        Svc.Obs.notify("weave:service:start-over:finish");
+      }
+    ).then(null,
+      err => {
+        this._log.error("startOver failed to re-initialize the identity manager: " + err);
+        // Still send the observer notification so the current state is
+        // reflected in the UI.
+        Svc.Obs.notify("weave:service:start-over:finish");
+      }
+    );
   },
 
   persistLogin: function persistLogin() {
@@ -981,12 +990,8 @@ Sync11Service.prototype = {
       }
 
       // Ask the identity manager to explicitly login now.
-      this._log.info("Logging in the user.");
       let cb = Async.makeSpinningCallback();
-      this.identity.ensureLoggedIn().then(
-        () => cb(null),
-        err => cb(err || "ensureLoggedIn failed")
-      );
+      this.identity.ensureLoggedIn().then(cb, cb);
 
       // Just let any errors bubble up - they've more context than we do!
       cb.wait();
@@ -997,9 +1002,9 @@ Sync11Service.prototype = {
           && (username || password || passphrase)) {
         Svc.Obs.notify("weave:service:setup-complete");
       }
+      this._log.info("Logging in the user.");
       this._updateCachedURLs();
 
-      this._log.info("User logged in successfully - verifying login.");
       if (!this.verifyLogin()) {
         // verifyLogin sets the failure states here.
         throw "Login failed: " + this.status.login;
@@ -1064,49 +1069,11 @@ Sync11Service.prototype = {
     }
   },
 
-  // Note: returns false if we failed for a reason other than the server not yet
-  // supporting the api.
-  _fetchServerConfiguration() {
-    if (Svc.Prefs.get("APILevel") >= 2) {
-      // This is similar to _fetchInfo, but with different error handling.
-      // Only supported by later sync implementations.
-
-      let infoURL = this.userBaseURL + "info/configuration";
-      this._log.debug("Fetching server configuration", infoURL);
-      let configResponse;
-      try {
-        configResponse = this.resource(infoURL).get();
-      } catch (ex) {
-        // This is probably a network or similar error.
-        this._log.warn("Failed to fetch info/configuration", ex);
-        this.errorHandler.checkServerError(ex);
-        return false;
-      }
-
-      if (configResponse.status == 404) {
-        // This server doesn't support the URL yet - that's OK.
-        this._log.debug("info/configuration returned 404 - using default upload semantics");
-      } else if (configResponse.status != 200) {
-        this._log.warn(`info/configuration returned ${configResponse.status} - using default configuration`);
-        this.errorHandler.checkServerError(configResponse);
-        return false;
-      } else {
-        this.serverConfiguration = configResponse.obj;
-      }
-      this._log.trace("info/configuration for this server", this.serverConfiguration);
-    }
-    return true;
-  },
-
   // Stuff we need to do after login, before we can really do
   // anything (e.g. key setup).
   _remoteSetup: function _remoteSetup(infoResponse) {
     let reset = false;
 
-    if (!this._fetchServerConfiguration()) {
-      return false;
-    }
-
     this._log.debug("Fetching global metadata record");
     let meta = this.recordManager.get(this.metaURL);
 
@@ -1133,7 +1100,7 @@ Sync11Service.prototype = {
         return false;
       }
 
-      if (this.recordManager.response.status == 404) {
+      if (!this.recordManager.response.success || !newMeta) {
         this._log.debug("No meta/global record on the server. Creating one.");
         newMeta = new WBORecord("meta", "global");
         newMeta.payload.syncID = this.syncID;
@@ -1143,16 +1110,10 @@ Sync11Service.prototype = {
         newMeta.isNew = true;
 
         this.recordManager.set(this.metaURL, newMeta);
-        let uploadRes = newMeta.upload(this.resource(this.metaURL));
-        if (!uploadRes.success) {
+        if (!newMeta.upload(this.resource(this.metaURL)).success) {
           this._log.warn("Unable to upload new meta/global. Failing remote setup.");
-          this.errorHandler.checkServerError(uploadRes);
           return false;
         }
-      } else if (!newMeta) {
-        this._log.warn("Unable to get meta/global. Failing remote setup.");
-        this.errorHandler.checkServerError(this.recordManager.response);
-        return false;
       } else {
         // If newMeta, then it stands to reason that meta != null.
         newMeta.isNew   = meta.isNew;
@@ -1293,9 +1254,13 @@ Sync11Service.prototype = {
     return reason;
   },
 
-  sync: function sync(engineNamesToSync) {
-    let dateStr = Utils.formatTimestamp(new Date());
-    this._log.debug("User-Agent: " + Utils.userAgent);
+  sync: function sync() {
+    if (!this.enabled) {
+      this._log.debug("Not syncing as Sync is disabled.");
+      return;
+    }
+    let dateStr = new Date().toLocaleFormat(LOG_DATE_FORMAT);
+    this._log.debug("User-Agent: " + SyncStorageRequest.prototype.userAgent);
     this._log.info("Starting sync at " + dateStr);
     this._catch(function () {
       // Make sure we're logged in.
@@ -1309,14 +1274,14 @@ Sync11Service.prototype = {
       else {
         this._log.trace("In sync: no need to login.");
       }
-      return this._lockedSync(engineNamesToSync);
+      return this._lockedSync.apply(this, arguments);
     })();
   },
 
   /**
    * Sync up engines with the server.
    */
-  _lockedSync: function _lockedSync(engineNamesToSync) {
+  _lockedSync: function _lockedSync() {
     return this._lock("service.js: sync",
                       this._notify("sync", "", function onNotify() {
 
@@ -1327,7 +1292,7 @@ Sync11Service.prototype = {
       let cb = Async.makeSpinningCallback();
       synchronizer.onComplete = cb;
 
-      synchronizer.sync(engineNamesToSync);
+      synchronizer.sync();
       // wait() throws if the first argument is truthy, which is exactly what
       // we want.
       let result = cb.wait();
@@ -1338,31 +1303,27 @@ Sync11Service.prototype = {
       // We successfully synchronized.
       // Check if the identity wants to pre-fetch a migration sentinel from
       // the server.
-      // Only supported by Sync server API level 2+
       // If we have no clusterURL, we are probably doing a node reassignment
       // so don't attempt to get it in that case.
-      if (Svc.Prefs.get("APILevel") >= 2 && this.clusterURL) {
-        this.identity.prefetchMigrationSentinel(this);
+      //if (this.clusterURL) {
+      //  this.identity.prefetchMigrationSentinel(this);
+      //}
+
+      // Now let's update our declined engines.
+      let meta = this.recordManager.get(this.metaURL);
+      if (!meta) {
+        this._log.warn("No meta/global; can't update declined state.");
+        return;
       }
 
-      // Now let's update our declined engines (but only if we have a metaURL;
-      // if Sync failed due to no node we will not have one)
-      if (this.metaURL) {
-        let meta = this.recordManager.get(this.metaURL);
-        if (!meta) {
-          this._log.warn("No meta/global; can't update declined state.");
-          return;
-        }
-
-        let declinedEngines = new DeclinedEngines(this);
-        let didChange = declinedEngines.updateDeclined(meta, this.engineManager);
-        if (!didChange) {
-          this._log.info("No change to declined engines. Not reuploading meta/global.");
-          return;
-        }
-
-        this.uploadMetaGlobal(meta);
+      let declinedEngines = new DeclinedEngines(this);
+      let didChange = declinedEngines.updateDeclined(meta, this.engineManager);
+      if (!didChange) {
+        this._log.info("No change to declined engines. Not reuploading meta/global.");
+        return;
       }
+
+      this.uploadMetaGlobal(meta);
     }))();
   },
 
@@ -1536,7 +1497,7 @@ Sync11Service.prototype = {
 
     // Wipe everything we know about except meta because we just uploaded it
     let engines = [this.clientsEngine].concat(this.engineManager.getAll());
-    let collections = engines.map(engine => engine.name);
+    let collections = [engine.name for each (engine in engines)];
     // TODO: there's a bug here. We should be calling resetClient, no?
 
     // Generate, upload, and download new keys. Do this last so we don't wipe
@@ -1555,7 +1516,6 @@ Sync11Service.prototype = {
    */
   wipeServer: function wipeServer(collections) {
     let response;
-    let histogram = Services.telemetry.getHistogramById("WEAVE_WIPE_SERVER_SUCCEEDED");
     if (!collections) {
       // Strip the trailing slash.
       let res = this.resource(this.storageURL.slice(0, -1));
@@ -1563,17 +1523,14 @@ Sync11Service.prototype = {
       try {
         response = res.delete();
       } catch (ex) {
-        this._log.debug("Failed to wipe server", ex);
-        histogram.add(false);
+        this._log.debug("Failed to wipe server: " + CommonUtils.exceptionStr(ex));
         throw ex;
       }
       if (response.status != 200 && response.status != 404) {
         this._log.debug("Aborting wipeServer. Server responded with " +
                         response.status + " response for " + this.storageURL);
-        histogram.add(false);
         throw response;
       }
-      histogram.add(true);
       return response.headers["x-weave-timestamp"];
     }
 
@@ -1583,15 +1540,14 @@ Sync11Service.prototype = {
       try {
         response = this.resource(url).delete();
       } catch (ex) {
-        this._log.debug("Failed to wipe '" + name + "' collection", ex);
-        histogram.add(false);
+        this._log.debug("Failed to wipe '" + name + "' collection: " +
+                        Utils.exceptionStr(ex));
         throw ex;
       }
 
       if (response.status != 200 && response.status != 404) {
         this._log.debug("Aborting wipeServer. Server responded with " +
                         response.status + " response for " + url);
-        histogram.add(false);
         throw response;
       }
 
@@ -1599,7 +1555,7 @@ Sync11Service.prototype = {
         timestamp = response.headers["x-weave-timestamp"];
       }
     }
-    histogram.add(true);
+
     return timestamp;
   },
 
@@ -1623,7 +1579,7 @@ Sync11Service.prototype = {
     }
 
     // Fully wipe each engine if it's able to decrypt data
-    for (let engine of engines) {
+    for each (let engine in engines) {
       if (engine.canDecrypt()) {
         engine.wipeClient();
       }
@@ -1701,7 +1657,7 @@ Sync11Service.prototype = {
       }
 
       // Have each engine drop any temporary meta data
-      for (let engine of engines) {
+      for each (let engine in engines) {
         engine.resetClient();
       }
     })();
@@ -1731,7 +1687,8 @@ Sync11Service.prototype = {
     return this.getStorageRequest(url).get(function onComplete(error) {
       // Note: 'this' is the request.
       if (error) {
-        this._log.debug("Failed to retrieve '" + info_type + "'", error);
+        this._log.debug("Failed to retrieve '" + info_type + "': " +
+                        Utils.exceptionStr(error));
         return callback(error);
       }
       if (this.response.status != 200) {
diff --git a/services/sync/modules/stages/cluster.js b/services/sync/modules/stages/cluster.js
index 7665ce825..dd358bf98 100644
--- a/services/sync/modules/stages/cluster.js
+++ b/services/sync/modules/stages/cluster.js
@@ -4,7 +4,7 @@
 
 this.EXPORTED_SYMBOLS = ["ClusterManager"];
 
-var {utils: Cu} = Components;
+const {utils: Cu} = Components;
 
 Cu.import("resource://gre/modules/Log.jsm");
 Cu.import("resource://services-sync/constants.js");
@@ -80,9 +80,6 @@ ClusterManager.prototype = {
       return false;
     }
 
-    // Convert from the funky "String object with additional properties" that
-    // resource.js returns to a plain-old string.
-    cluster = cluster.toString();
     // Don't update stuff if we already have the right cluster
     if (cluster == this.service.clusterURL) {
       return false;
@@ -90,6 +87,7 @@ ClusterManager.prototype = {
 
     this._log.debug("Setting cluster to " + cluster);
     this.service.clusterURL = cluster;
+    Svc.Prefs.set("lastClusterUpdate", Date.now().toString());
 
     return true;
   },
diff --git a/services/sync/modules/stages/declined.js b/services/sync/modules/stages/declined.js
index ff8a14181..b0877e929 100644
--- a/services/sync/modules/stages/declined.js
+++ b/services/sync/modules/stages/declined.js
@@ -11,7 +11,7 @@
 
 this.EXPORTED_SYMBOLS = ["DeclinedEngines"];
 
-var {utils: Cu} = Components;
+const {utils: Cu} = Components;
 
 Cu.import("resource://services-sync/constants.js");
 Cu.import("resource://gre/modules/Log.jsm");
@@ -29,8 +29,8 @@ this.DeclinedEngines = function (service) {
 }
 this.DeclinedEngines.prototype = {
   updateDeclined: function (meta, engineManager=this.service.engineManager) {
-    let enabled = new Set(engineManager.getEnabled().map(e => e.name));
-    let known = new Set(engineManager.getAll().map(e => e.name));
+    let enabled = new Set([e.name for each (e in engineManager.getEnabled())]);
+    let known = new Set([e.name for each (e in engineManager.getAll())]);
     let remoteDeclined = new Set(meta.payload.declined || []);
     let localDeclined = new Set(engineManager.getDeclined());
 
diff --git a/services/sync/modules/stages/enginesync.js b/services/sync/modules/stages/enginesync.js
index a00a2f48b..ed91adddb 100644
--- a/services/sync/modules/stages/enginesync.js
+++ b/services/sync/modules/stages/enginesync.js
@@ -8,16 +8,13 @@
 
 this.EXPORTED_SYMBOLS = ["EngineSynchronizer"];
 
-var {utils: Cu} = Components;
+const {utils: Cu} = Components;
 
 Cu.import("resource://gre/modules/Log.jsm");
 Cu.import("resource://services-sync/constants.js");
 Cu.import("resource://services-sync/engines.js");
 Cu.import("resource://services-sync/policies.js");
 Cu.import("resource://services-sync/util.js");
-Cu.import("resource://services-common/observers.js");
-Cu.import("resource://services-common/async.js");
-Cu.import("resource://gre/modules/Task.jsm");
 
 /**
  * Perform synchronization of engines.
@@ -34,7 +31,7 @@ this.EngineSynchronizer = function EngineSynchronizer(service) {
 }
 
 EngineSynchronizer.prototype = {
-  sync: function sync(engineNamesToSync) {
+  sync: function sync() {
     if (!this.onComplete) {
       throw new Error("onComplete handler not installed.");
     }
@@ -99,9 +96,6 @@ EngineSynchronizer.prototype = {
       return;
     }
 
-    // We only honor the "hint" of what engines to Sync if this isn't
-    // a first sync.
-    let allowEnginesHint = false;
     // Wipe data in the desired direction if necessary
     switch (Svc.Prefs.get("firstSync")) {
       case "resetClient":
@@ -113,9 +107,6 @@ EngineSynchronizer.prototype = {
       case "wipeRemote":
         this.service.wipeRemote(engineManager.enabledEngineNames);
         break;
-      default:
-        allowEnginesHint = true;
-        break;
     }
 
     if (this.service.clientsEngine.localCommands) {
@@ -145,31 +136,20 @@ EngineSynchronizer.prototype = {
     try {
       this._updateEnabledEngines();
     } catch (ex) {
-      this._log.debug("Updating enabled engines failed", ex);
+      this._log.debug("Updating enabled engines failed: " +
+                      Utils.exceptionStr(ex));
       this.service.errorHandler.checkServerError(ex);
       this.onComplete(ex);
       return;
     }
 
-    // If the engines to sync has been specified, we sync in the order specified.
-    let enginesToSync;
-    if (allowEnginesHint && engineNamesToSync) {
-      this._log.info("Syncing specified engines", engineNamesToSync);
-      enginesToSync = engineManager.get(engineNamesToSync).filter(e => e.enabled);
-    } else {
-      this._log.info("Syncing all enabled engines.");
-      enginesToSync = engineManager.getEnabled();
-    }
     try {
-      // We don't bother validating engines that failed to sync.
-      let enginesToValidate = [];
-      for (let engine of enginesToSync) {
+      for (let engine of engineManager.getEnabled()) {
         // If there's any problems with syncing the engine, report the failure
         if (!(this._syncEngine(engine)) || this.service.status.enforceBackoff) {
           this._log.info("Aborting sync for failure in " + engine.name);
           break;
         }
-        enginesToValidate.push(engine);
       }
 
       // If _syncEngine fails for a 401, we might not have a cluster URL here.
@@ -195,8 +175,6 @@ EngineSynchronizer.prototype = {
         }
       }
 
-      Async.promiseSpinningly(this._tryValidateEngines(enginesToValidate));
-
       // If there were no sync engine failures
       if (this.service.status.service != SYNC_FAILED_PARTIAL) {
         Svc.Prefs.set("lastSync", new Date().toString());
@@ -206,7 +184,7 @@ EngineSynchronizer.prototype = {
       Svc.Prefs.reset("firstSync");
 
       let syncTime = ((Date.now() - startTime) / 1000).toFixed(2);
-      let dateStr = Utils.formatTimestamp(new Date());
+      let dateStr = new Date().toLocaleFormat(LOG_DATE_FORMAT);
       this._log.info("Sync completed at " + dateStr
                      + " after " + syncTime + " secs.");
     }
@@ -214,106 +192,6 @@ EngineSynchronizer.prototype = {
     this.onComplete(null);
   },
 
-  _tryValidateEngines: Task.async(function* (recentlySyncedEngines) {
-    if (!Services.telemetry.canRecordBase || !Svc.Prefs.get("validation.enabled", false)) {
-      this._log.info("Skipping validation: validation or telemetry reporting is disabled");
-      return;
-    }
-
-    let lastValidation = Svc.Prefs.get("validation.lastTime", 0);
-    let validationInterval = Svc.Prefs.get("validation.interval");
-    let nowSeconds = Math.floor(Date.now() / 1000);
-
-    if (nowSeconds - lastValidation < validationInterval) {
-      this._log.info("Skipping validation: too recent since last validation attempt");
-      return;
-    }
-    // Update the time now, even if we may return false still. We don't want to
-    // check the rest of these more frequently than once a day.
-    Svc.Prefs.set("validation.lastTime", nowSeconds);
-
-    // Validation only occurs a certain percentage of the time.
-    let validationProbability = Svc.Prefs.get("validation.percentageChance", 0) / 100.0;
-    if (validationProbability < Math.random()) {
-      this._log.info("Skipping validation: Probability threshold not met");
-      return;
-    }
-    let maxRecords = Svc.Prefs.get("validation.maxRecords");
-    if (!maxRecords) {
-      // Don't bother asking the server for the counts if we know validation
-      // won't happen anyway.
-      return;
-    }
-
-    // maxRecords of -1 means "any number", so we can skip asking the server.
-    // Used for tests.
-    let info;
-    if (maxRecords < 0) {
-      info = {};
-      for (let e of recentlySyncedEngines) {
-        info[e.name] = 1; // needs to be < maxRecords
-      }
-      maxRecords = 2;
-    } else {
-
-      let collectionCountsURL = this.service.userBaseURL + "info/collection_counts";
-      try {
-        let infoResp = this.service._fetchInfo(collectionCountsURL);
-        if (!infoResp.success) {
-          this._log.error("Can't run validation: request to info/collection_counts responded with "
-                          + resp.status);
-          return;
-        }
-        info = infoResp.obj; // might throw because obj is a getter which parses json.
-      } catch (e) {
-        // Not running validation is totally fine, so we just write an error log and return.
-        this._log.error("Can't run validation: Caught error when fetching counts", e);
-        return;
-      }
-    }
-
-    if (!info) {
-      return;
-    }
-
-    let engineLookup = new Map(recentlySyncedEngines.map(e => [e.name, e]));
-    let toRun = [];
-    for (let [engineName, recordCount] of Object.entries(info)) {
-      let engine = engineLookup.get(engineName);
-      if (recordCount > maxRecords || !engine) {
-        this._log.debug(`Skipping validation for ${engineName} because it's not an engine or ` +
-                        `the number of records (${recordCount}) is greater than the maximum allowed (${maxRecords}).`);
-        continue;
-      }
-      let validator = engine.getValidator();
-      if (!validator) {
-        continue;
-      }
-      // Put this in an array so that we know how many we're going to do, so we
-      // don't tell users we're going to run some validators when we aren't.
-      toRun.push({ engine, validator });
-    }
-
-    if (!toRun.length) {
-      return;
-    }
-    Services.console.logStringMessage(
-      "Sync is about to run a consistency check. This may be slow, and " +
-      "can be controlled using the pref \"services.sync.validation.enabled\".\n" +
-      "If you encounter any problems because of this, please file a bug.");
-    for (let { validator, engine } of toRun) {
-      try {
-        let result = yield validator.validate(engine);
-        Observers.notify("weave:engine:validate:finish", result, engine.name);
-      } catch (e) {
-        this._log.error(`Failed to run validation on ${engine.name}!`, e);
-        Observers.notify("weave:engine:validate:error", e, engine.name)
-        // Keep validating -- there's no reason to think that a failure for one
-        // validator would mean the others will fail.
-      }
-    }
-  }),
-
   // Returns true if sync should proceed.
   // false / no return value means sync should be aborted.
   _syncEngine: function _syncEngine(engine) {
@@ -346,15 +224,8 @@ EngineSynchronizer.prototype = {
     // If we're the only client, and no engines are marked as enabled,
     // thumb our noses at the server data: it can't be right.
     // Belt-and-suspenders approach to Bug 615926.
-    let hasEnabledEngines = false;
-    for (let e in meta.payload.engines) {
-      if (e != "clients") {
-        hasEnabledEngines = true;
-        break;
-      }
-    }
-
-    if ((numClients <= 1) && !hasEnabledEngines) {
+    if ((numClients <= 1) &&
+        ([e for (e in meta.payload.engines) if (e != "clients")].length == 0)) {
       this._log.info("One client and no enabled engines: not touching local engine status.");
       return;
     }
@@ -418,7 +289,7 @@ EngineSynchronizer.prototype = {
     }
 
     // Any remaining engines were either enabled locally or disabled remotely.
-    for (let engineName of enabled) {
+    for each (let engineName in enabled) {
       let engine = engineManager.get(engineName);
       if (Svc.Prefs.get("engineStatusChanged." + engine.prefName, false)) {
         this._log.trace("The " + engineName + " engine was enabled locally.");
diff --git a/services/sync/modules/status.js b/services/sync/modules/status.js
index 100bc7965..19dff9712 100644
--- a/services/sync/modules/status.js
+++ b/services/sync/modules/status.js
@@ -4,10 +4,10 @@
 
 this.EXPORTED_SYMBOLS = ["Status"];
 
-var Cc = Components.classes;
-var Ci = Components.interfaces;
-var Cr = Components.results;
-var Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+const Cu = Components.utils;
 
 Cu.import("resource://services-sync/constants.js");
 Cu.import("resource://gre/modules/Log.jsm");
@@ -30,7 +30,10 @@ this.Status = {
                     .wrappedJSObject;
     let idClass = service.fxAccountsEnabled ? BrowserIDManager : IdentityManager;
     this.__authManager = new idClass();
-    this.__authManager.initialize();
+    // .initialize returns a promise, so we need to spin until it resolves.
+    let cb = Async.makeSpinningCallback();
+    this.__authManager.initialize().then(cb, cb);
+    cb.wait();
     return this.__authManager;
   },
 
diff --git a/services/sync/modules/telemetry.js b/services/sync/modules/telemetry.js
deleted file mode 100644
index c311387f7..000000000
--- a/services/sync/modules/telemetry.js
+++ /dev/null
@@ -1,578 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-"use strict";
-
-const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
-
-this.EXPORTED_SYMBOLS = ["SyncTelemetry"];
-
-Cu.import("resource://services-sync/browserid_identity.js");
-Cu.import("resource://services-sync/main.js");
-Cu.import("resource://services-sync/status.js");
-Cu.import("resource://services-sync/util.js");
-Cu.import("resource://services-common/observers.js");
-Cu.import("resource://services-common/async.js");
-Cu.import("resource://gre/modules/Log.jsm");
-Cu.import("resource://gre/modules/TelemetryController.jsm");
-Cu.import("resource://gre/modules/FxAccounts.jsm");
-Cu.import("resource://gre/modules/XPCOMUtils.jsm");
-Cu.import("resource://gre/modules/osfile.jsm", this);
-
-let constants = {};
-Cu.import("resource://services-sync/constants.js", constants);
-
-var fxAccountsCommon = {};
-Cu.import("resource://gre/modules/FxAccountsCommon.js", fxAccountsCommon);
-
-XPCOMUtils.defineLazyServiceGetter(this, "Telemetry",
-                                   "@mozilla.org/base/telemetry;1",
-                                   "nsITelemetry");
-
-const log = Log.repository.getLogger("Sync.Telemetry");
-
-const TOPICS = [
-  "profile-before-change",
-  "weave:service:sync:start",
-  "weave:service:sync:finish",
-  "weave:service:sync:error",
-
-  "weave:engine:sync:start",
-  "weave:engine:sync:finish",
-  "weave:engine:sync:error",
-  "weave:engine:sync:applied",
-  "weave:engine:sync:uploaded",
-  "weave:engine:validate:finish",
-  "weave:engine:validate:error",
-];
-
-const PING_FORMAT_VERSION = 1;
-
-// The set of engines we record telemetry for - any other engines are ignored.
-const ENGINES = new Set(["addons", "bookmarks", "clients", "forms", "history",
-                         "passwords", "prefs", "tabs", "extension-storage"]);
-
-// A regex we can use to replace the profile dir in error messages. We use a
-// regexp so we can simply replace all case-insensitive occurences.
-// This escaping function is from:
-// https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions
-const reProfileDir = new RegExp(
-        OS.Constants.Path.profileDir.replace(/[.*+?^${}()|[\]\\]/g, "\\$&"),
-        "gi");
-
-function transformError(error, engineName) {
-  if (Async.isShutdownException(error)) {
-    return { name: "shutdownerror" };
-  }
-
-  if (typeof error === "string") {
-    if (error.startsWith("error.")) {
-      // This is hacky, but I can't imagine that it's not also accurate.
-      return { name: "othererror", error };
-    }
-    // There's a chance the profiledir is in the error string which is PII we
-    // want to avoid including in the ping.
-    error = error.replace(reProfileDir, "[profileDir]");
-    return { name: "unexpectederror", error };
-  }
-
-  if (error.failureCode) {
-    return { name: "othererror", error: error.failureCode };
-  }
-
-  if (error instanceof AuthenticationError) {
-    return { name: "autherror", from: error.source };
-  }
-
-  if (error instanceof Ci.mozIStorageError) {
-    return { name: "sqlerror", code: error.result };
-  }
-
-  let httpCode = error.status ||
-    (error.response && error.response.status) ||
-    error.code;
-
-  if (httpCode) {
-    return { name: "httperror", code: httpCode };
-  }
-
-  if (error.result) {
-    return { name: "nserror", code: error.result };
-  }
-
-  return {
-    name: "unexpectederror",
-    // as above, remove the profile dir value.
-    error: String(error).replace(reProfileDir, "[profileDir]")
-  }
-}
-
-function tryGetMonotonicTimestamp() {
-  try {
-    return Telemetry.msSinceProcessStart();
-  } catch (e) {
-    log.warn("Unable to get a monotonic timestamp!");
-    return -1;
-  }
-}
-
-function timeDeltaFrom(monotonicStartTime) {
-  let now = tryGetMonotonicTimestamp();
-  if (monotonicStartTime !== -1 && now !== -1) {
-    return Math.round(now - monotonicStartTime);
-  }
-  return -1;
-}
-
-class EngineRecord {
-  constructor(name) {
-    // startTime is in ms from process start, but is monotonic (unlike Date.now())
-    // so we need to keep both it and when.
-    this.startTime = tryGetMonotonicTimestamp();
-    this.name = name;
-  }
-
-  toJSON() {
-    let result = Object.assign({}, this);
-    delete result.startTime;
-    return result;
-  }
-
-  finished(error) {
-    let took = timeDeltaFrom(this.startTime);
-    if (took > 0) {
-      this.took = took;
-    }
-    if (error) {
-      this.failureReason = transformError(error, this.name);
-    }
-  }
-
-  recordApplied(counts) {
-    if (this.incoming) {
-      log.error(`Incoming records applied multiple times for engine ${this.name}!`);
-      return;
-    }
-    if (this.name === "clients" && !counts.failed) {
-      // ignore successful application of client records
-      // since otherwise they show up every time and are meaningless.
-      return;
-    }
-
-    let incomingData = {};
-    let properties = ["applied", "failed", "newFailed", "reconciled"];
-    // Only record non-zero properties and only record incoming at all if
-    // there's at least one property we care about.
-    for (let property of properties) {
-      if (counts[property]) {
-        incomingData[property] = counts[property];
-        this.incoming = incomingData;
-      }
-    }
-  }
-
-  recordValidation(validationResult) {
-    if (this.validation) {
-      log.error(`Multiple validations occurred for engine ${this.name}!`);
-      return;
-    }
-    let { problems, version, duration, recordCount } = validationResult;
-    let validation = {
-      version: version || 0,
-      checked: recordCount || 0,
-    };
-    if (duration > 0) {
-      validation.took = Math.round(duration);
-    }
-    let summarized = problems.getSummary(true).filter(({count}) => count > 0);
-    if (summarized.length) {
-      validation.problems = summarized;
-    }
-    this.validation = validation;
-  }
-
-  recordValidationError(e) {
-    if (this.validation) {
-      log.error(`Multiple validations occurred for engine ${this.name}!`);
-      return;
-    }
-
-    this.validation = {
-      failureReason: transformError(e)
-    };
-  }
-
-  recordUploaded(counts) {
-    if (counts.sent || counts.failed) {
-      if (!this.outgoing) {
-        this.outgoing = [];
-      }
-      this.outgoing.push({
-        sent: counts.sent || undefined,
-        failed: counts.failed || undefined,
-      });
-    }
-  }
-}
-
-class TelemetryRecord {
-  constructor(allowedEngines) {
-    this.allowedEngines = allowedEngines;
-    // Our failure reason. This property only exists in the generated ping if an
-    // error actually occurred.
-    this.failureReason = undefined;
-    this.uid = "";
-    this.when = Date.now();
-    this.startTime = tryGetMonotonicTimestamp();
-    this.took = 0; // will be set later.
-
-    // All engines that have finished (ie, does not include the "current" one)
-    // We omit this from the ping if it's empty.
-    this.engines = [];
-    // The engine that has started but not yet stopped.
-    this.currentEngine = null;
-  }
-
-  toJSON() {
-    let result = {
-      when: this.when,
-      uid: this.uid,
-      took: this.took,
-      failureReason: this.failureReason,
-      status: this.status,
-      deviceID: this.deviceID,
-      devices: this.devices,
-    };
-    let engines = [];
-    for (let engine of this.engines) {
-      engines.push(engine.toJSON());
-    }
-    if (engines.length > 0) {
-      result.engines = engines;
-    }
-    return result;
-  }
-
-  finished(error) {
-    this.took = timeDeltaFrom(this.startTime);
-    if (this.currentEngine != null) {
-      log.error("Finished called for the sync before the current engine finished");
-      this.currentEngine.finished(null);
-      this.onEngineStop(this.currentEngine.name);
-    }
-    if (error) {
-      this.failureReason = transformError(error);
-    }
-
-    // We don't bother including the "devices" field if we can't come up with a
-    // UID or device ID for *this* device -- If that's the case, any data we'd
-    // put there would be likely to be full of garbage anyway.
-    let includeDeviceInfo = false;
-    try {
-      this.uid = Weave.Service.identity.hashedUID();
-      let deviceID = Weave.Service.identity.deviceID();
-      if (deviceID) {
-        // Combine the raw device id with the metrics uid to create a stable
-        // unique identifier that can't be mapped back to the user's FxA
-        // identity without knowing the metrics HMAC key.
-        this.deviceID = Utils.sha256(deviceID + this.uid);
-        includeDeviceInfo = true;
-      }
-    } catch (e) {
-      this.uid = "0".repeat(32);
-      this.deviceID = undefined;
-    }
-
-    if (includeDeviceInfo) {
-      let remoteDevices = Weave.Service.clientsEngine.remoteClients;
-      this.devices = remoteDevices.map(device => {
-        return {
-          os: device.os,
-          version: device.version,
-          id: Utils.sha256(device.id + this.uid)
-        };
-      });
-    }
-
-    // Check for engine statuses. -- We do this now, and not in engine.finished
-    // to make sure any statuses that get set "late" are recorded
-    for (let engine of this.engines) {
-      let status = Status.engines[engine.name];
-      if (status && status !== constants.ENGINE_SUCCEEDED) {
-        engine.status = status;
-      }
-    }
-
-    let statusObject = {};
-
-    let serviceStatus = Status.service;
-    if (serviceStatus && serviceStatus !== constants.STATUS_OK) {
-      statusObject.service = serviceStatus;
-      this.status = statusObject;
-    }
-    let syncStatus = Status.sync;
-    if (syncStatus && syncStatus !== constants.SYNC_SUCCEEDED) {
-      statusObject.sync = syncStatus;
-      this.status = statusObject;
-    }
-  }
-
-  onEngineStart(engineName) {
-    if (this._shouldIgnoreEngine(engineName, false)) {
-      return;
-    }
-
-    if (this.currentEngine) {
-      log.error(`Being told that engine ${engineName} has started, but current engine ${
-        this.currentEngine.name} hasn't stopped`);
-      // Just discard the current engine rather than making up data for it.
-    }
-    this.currentEngine = new EngineRecord(engineName);
-  }
-
-  onEngineStop(engineName, error) {
-    // We only care if it's the current engine if we have a current engine.
-    if (this._shouldIgnoreEngine(engineName, !!this.currentEngine)) {
-      return;
-    }
-    if (!this.currentEngine) {
-      // It's possible for us to get an error before the start message of an engine
-      // (somehow), in which case we still want to record that error.
-      if (!error) {
-        return;
-      }
-      log.error(`Error triggered on ${engineName} when no current engine exists: ${error}`);
-      this.currentEngine = new EngineRecord(engineName);
-    }
-    this.currentEngine.finished(error);
-    this.engines.push(this.currentEngine);
-    this.currentEngine = null;
-  }
-
-  onEngineApplied(engineName, counts) {
-    if (this._shouldIgnoreEngine(engineName)) {
-      return;
-    }
-    this.currentEngine.recordApplied(counts);
-  }
-
-  onEngineValidated(engineName, validationData) {
-    if (this._shouldIgnoreEngine(engineName, false)) {
-      return;
-    }
-    let engine = this.engines.find(e => e.name === engineName);
-    if (!engine && this.currentEngine && engineName === this.currentEngine.name) {
-      engine = this.currentEngine;
-    }
-    if (engine) {
-      engine.recordValidation(validationData);
-    } else {
-      log.warn(`Validation event triggered for engine ${engineName}, which hasn't been synced!`);
-    }
-  }
-
-  onEngineValidateError(engineName, error) {
-    if (this._shouldIgnoreEngine(engineName, false)) {
-      return;
-    }
-    let engine = this.engines.find(e => e.name === engineName);
-    if (!engine && this.currentEngine && engineName === this.currentEngine.name) {
-      engine = this.currentEngine;
-    }
-    if (engine) {
-      engine.recordValidationError(error);
-    } else {
-      log.warn(`Validation failure event triggered for engine ${engineName}, which hasn't been synced!`);
-    }
-  }
-
-  onEngineUploaded(engineName, counts) {
-    if (this._shouldIgnoreEngine(engineName)) {
-      return;
-    }
-    this.currentEngine.recordUploaded(counts);
-  }
-
-  _shouldIgnoreEngine(engineName, shouldBeCurrent = true) {
-    if (!this.allowedEngines.has(engineName)) {
-      log.info(`Notification for engine ${engineName}, but we aren't recording telemetry for it`);
-      return true;
-    }
-    if (shouldBeCurrent) {
-      if (!this.currentEngine || engineName != this.currentEngine.name) {
-        log.error(`Notification for engine ${engineName} but it isn't current`);
-        return true;
-      }
-    }
-    return false;
-  }
-}
-
-class SyncTelemetryImpl {
-  constructor(allowedEngines) {
-    log.level = Log.Level[Svc.Prefs.get("log.logger.telemetry", "Trace")];
-    // This is accessible so we can enable custom engines during tests.
-    this.allowedEngines = allowedEngines;
-    this.current = null;
-    this.setupObservers();
-
-    this.payloads = [];
-    this.discarded = 0;
-    this.maxPayloadCount = Svc.Prefs.get("telemetry.maxPayloadCount");
-    this.submissionInterval = Svc.Prefs.get("telemetry.submissionInterval") * 1000;
-    this.lastSubmissionTime = Telemetry.msSinceProcessStart();
-  }
-
-  getPingJSON(reason) {
-    return {
-      why: reason,
-      discarded: this.discarded || undefined,
-      version: PING_FORMAT_VERSION,
-      syncs: this.payloads.slice(),
-    };
-  }
-
-  finish(reason) {
-    // Note that we might be in the middle of a sync right now, and so we don't
-    // want to touch this.current.
-    let result = this.getPingJSON(reason);
-    this.payloads = [];
-    this.discarded = 0;
-    this.submit(result);
-  }
-
-  setupObservers() {
-    for (let topic of TOPICS) {
-      Observers.add(topic, this, this);
-    }
-  }
-
-  shutdown() {
-    this.finish("shutdown");
-    for (let topic of TOPICS) {
-      Observers.remove(topic, this, this);
-    }
-  }
-
-  submit(record) {
-    // We still call submit() with possibly illegal payloads so that tests can
-    // know that the ping was built. We don't end up submitting them, however.
-    if (record.syncs.length) {
-      log.trace(`submitting ${record.syncs.length} sync record(s) to telemetry`);
-      TelemetryController.submitExternalPing("sync", record);
-    }
-  }
-
-
-  onSyncStarted() {
-    if (this.current) {
-      log.warn("Observed weave:service:sync:start, but we're already recording a sync!");
-      // Just discard the old record, consistent with our handling of engines, above.
-      this.current = null;
-    }
-    this.current = new TelemetryRecord(this.allowedEngines);
-  }
-
-  _checkCurrent(topic) {
-    if (!this.current) {
-      log.warn(`Observed notification ${topic} but no current sync is being recorded.`);
-      return false;
-    }
-    return true;
-  }
-
-  onSyncFinished(error) {
-    if (!this.current) {
-      log.warn("onSyncFinished but we aren't recording");
-      return;
-    }
-    this.current.finished(error);
-    if (this.payloads.length < this.maxPayloadCount) {
-      this.payloads.push(this.current.toJSON());
-    } else {
-      ++this.discarded;
-    }
-    this.current = null;
-    if ((Telemetry.msSinceProcessStart() - this.lastSubmissionTime) > this.submissionInterval) {
-      this.finish("schedule");
-      this.lastSubmissionTime = Telemetry.msSinceProcessStart();
-    }
-  }
-
-  observe(subject, topic, data) {
-    log.trace(`observed ${topic} ${data}`);
-
-    switch (topic) {
-      case "profile-before-change":
-        this.shutdown();
-        break;
-
-      /* sync itself state changes */
-      case "weave:service:sync:start":
-        this.onSyncStarted();
-        break;
-
-      case "weave:service:sync:finish":
-        if (this._checkCurrent(topic)) {
-          this.onSyncFinished(null);
-        }
-        break;
-
-      case "weave:service:sync:error":
-        // argument needs to be truthy (this should always be the case)
-        this.onSyncFinished(subject || "Unknown");
-        break;
-
-      /* engine sync state changes */
-      case "weave:engine:sync:start":
-        if (this._checkCurrent(topic)) {
-          this.current.onEngineStart(data);
-        }
-        break;
-      case "weave:engine:sync:finish":
-        if (this._checkCurrent(topic)) {
-          this.current.onEngineStop(data, null);
-        }
-        break;
-
-      case "weave:engine:sync:error":
-        if (this._checkCurrent(topic)) {
-          // argument needs to be truthy (this should always be the case)
-          this.current.onEngineStop(data, subject || "Unknown");
-        }
-        break;
-
-      /* engine counts */
-      case "weave:engine:sync:applied":
-        if (this._checkCurrent(topic)) {
-          this.current.onEngineApplied(data, subject);
-        }
-        break;
-
-      case "weave:engine:sync:uploaded":
-        if (this._checkCurrent(topic)) {
-          this.current.onEngineUploaded(data, subject);
-        }
-        break;
-
-      case "weave:engine:validate:finish":
-        if (this._checkCurrent(topic)) {
-          this.current.onEngineValidated(data, subject);
-        }
-        break;
-
-      case "weave:engine:validate:error":
-        if (this._checkCurrent(topic)) {
-          this.current.onEngineValidateError(data, subject || "Unknown");
-        }
-        break;
-
-      default:
-        log.warn(`unexpected observer topic ${topic}`);
-        break;
-    }
-  }
-}
-
-this.SyncTelemetry = new SyncTelemetryImpl(ENGINES);
diff --git a/services/sync/modules/userapi.js b/services/sync/modules/userapi.js
index e906440bd..ec77d63e2 100644
--- a/services/sync/modules/userapi.js
+++ b/services/sync/modules/userapi.js
@@ -8,7 +8,7 @@ this.EXPORTED_SYMBOLS = [
   "UserAPI10Client",
 ];
 
-var {utils: Cu} = Components;
+const {utils: Cu} = Components;
 
 Cu.import("resource://gre/modules/Log.jsm");
 Cu.import("resource://services-common/rest.js");
diff --git a/services/sync/modules/util.js b/services/sync/modules/util.js
index e9dbcb37d..67cc3f063 100644
--- a/services/sync/modules/util.js
+++ b/services/sync/modules/util.js
@@ -4,7 +4,7 @@
 
 this.EXPORTED_SYMBOLS = ["XPCOMUtils", "Services", "Utils", "Async", "Svc", "Str"];
 
-var {classes: Cc, interfaces: Ci, results: Cr, utils: Cu} = Components;
+const {classes: Cc, interfaces: Ci, results: Cr, utils: Cu} = Components;
 
 Cu.import("resource://gre/modules/Log.jsm");
 Cu.import("resource://services-common/observers.js");
@@ -35,6 +35,8 @@ this.Utils = {
   // In the ideal world, references to these would be removed.
   nextTick: CommonUtils.nextTick,
   namedTimer: CommonUtils.namedTimer,
+  exceptionStr: CommonUtils.exceptionStr,
+  stackTrace: CommonUtils.stackTrace,
   makeURI: CommonUtils.makeURI,
   encodeUTF8: CommonUtils.encodeUTF8,
   decodeUTF8: CommonUtils.decodeUTF8,
@@ -52,7 +54,6 @@ this.Utils = {
   digestBytes: CryptoUtils.digestBytes,
   sha1: CryptoUtils.sha1,
   sha1Base32: CryptoUtils.sha1Base32,
-  sha256: CryptoUtils.sha256,
   makeHMACKey: CryptoUtils.makeHMACKey,
   makeHMACHasher: CryptoUtils.makeHMACHasher,
   hkdfExpand: CryptoUtils.hkdfExpand,
@@ -61,25 +62,6 @@ this.Utils = {
   getHTTPMACSHA1Header: CryptoUtils.getHTTPMACSHA1Header,
 
   /**
-   * The string to use as the base User-Agent in Sync requests.
-   * This string will look something like
-   *
-   *   Firefox/49.0a1 (Windows NT 6.1; WOW64; rv:46.0) FxSync/1.51.0.20160516142357.desktop
-   */
-  _userAgent: null,
-  get userAgent() {
-    if (!this._userAgent) {
-      let hph = Cc["@mozilla.org/network/protocol;1?name=http"].getService(Ci.nsIHttpProtocolHandler);
-      this._userAgent =
-        Services.appinfo.name + "/" + Services.appinfo.version +  // Product.
-        " (" + hph.oscpu + ")" +                                  // (oscpu)
-        " FxSync/" + WEAVE_VERSION + "." +                        // Sync.
-        Services.appinfo.appBuildID + ".";                        // Build.
-    }
-    return this._userAgent + Svc.Prefs.get("client.type", "desktop");
-  },
-
-  /**
    * Wrap a function to catch all exceptions and log them
    *
    * @usage MyObj._catch = Utils.catch;
@@ -95,7 +77,7 @@ this.Utils = {
         return func.call(thisArg);
       }
       catch(ex) {
-        thisArg._log.debug("Exception calling " + (func.name || "anonymous function"), ex);
+        thisArg._log.debug("Exception: " + Utils.exceptionStr(ex));
         if (exceptionCallback) {
           return exceptionCallback.call(thisArg, ex);
         }
@@ -271,14 +253,14 @@ this.Utils = {
    */
   base32ToFriendly: function base32ToFriendly(input) {
     return input.toLowerCase()
-                .replace(/l/g, '8')
-                .replace(/o/g, '9');
+                .replace("l", '8', "g")
+                .replace("o", '9', "g");
   },
 
   base32FromFriendly: function base32FromFriendly(input) {
     return input.toUpperCase()
-                .replace(/8/g, 'L')
-                .replace(/9/g, 'O');
+                .replace("8", 'L', "g")
+                .replace("9", 'O', "g");
   },
 
   /**
@@ -356,14 +338,12 @@ this.Utils = {
 
     try {
       json = yield CommonUtils.readJSON(path);
+    } catch (e if e instanceof OS.File.Error && e.becauseNoSuchFile) {
+      // Ignore non-existent files.
     } catch (e) {
-      if (e instanceof OS.File.Error && e.becauseNoSuchFile) {
-        // Ignore non-existent files, but explicitly return null.
-        json = null;
-      } else {
-        if (that._log) {
-          that._log.debug("Failed to load json", e);
-        }
+      if (that._log) {
+        that._log.debug("Failed to load json: " +
+                        CommonUtils.exceptionStr(e));
       }
     }
 
@@ -411,52 +391,6 @@ this.Utils = {
     }
   }),
 
-  /**
-   * Move a json file in the profile directory. Will fail if a file exists at the
-   * destination.
-   *
-   * @returns a promise that resolves to undefined on success, or rejects on failure
-   *
-   * @param aFrom
-   *        Current path to the JSON file saved on disk, relative to profileDir/weave
-   *        .json will be appended to the file name.
-   * @param aTo
-   *        New path to the JSON file saved on disk, relative to profileDir/weave
-   *        .json will be appended to the file name.
-   * @param that
-   *        Object to use for logging
-   */
-  jsonMove(aFrom, aTo, that) {
-    let pathFrom = OS.Path.join(OS.Constants.Path.profileDir, "weave",
-                                ...(aFrom + ".json").split("/"));
-    let pathTo = OS.Path.join(OS.Constants.Path.profileDir, "weave",
-                              ...(aTo + ".json").split("/"));
-    if (that._log) {
-      that._log.trace("Moving " + pathFrom + " to " + pathTo);
-    }
-    return OS.File.move(pathFrom, pathTo, { noOverwrite: true });
-  },
-
-  /**
-   * Removes a json file in the profile directory.
-   *
-   * @returns a promise that resolves to undefined on success, or rejects on failure
-   *
-   * @param filePath
-   *        Current path to the JSON file saved on disk, relative to profileDir/weave
-   *        .json will be appended to the file name.
-   * @param that
-   *        Object to use for logging
-   */
-  jsonRemove(filePath, that) {
-    let path = OS.Path.join(OS.Constants.Path.profileDir, "weave",
-                            ...(filePath + ".json").split("/"));
-    if (that._log) {
-      that._log.trace("Deleting " + path);
-    }
-    return OS.File.remove(path, { ignoreAbsent: true });
-  },
-
   getErrorString: function Utils_getErrorString(error, args) {
     try {
       return Str.errors.get(error, args || null);
@@ -543,7 +477,7 @@ this.Utils = {
 
     // 20-char sync key.
     if (pp.length == 23 &&
-        [5, 11, 17].every(i => pp[i] == '-')) {
+        [5, 11, 17].every(function(i) pp[i] == '-')) {
 
       return pp.slice(0, 5) + pp.slice(6, 11)
              + pp.slice(12, 17) + pp.slice(18, 23);
@@ -551,7 +485,7 @@ this.Utils = {
 
     // "Modern" 26-char key.
     if (pp.length == 31 &&
-        [1, 7, 13, 19, 25].every(i => pp[i] == '-')) {
+        [1, 7, 13, 19, 25].every(function(i) pp[i] == '-')) {
 
       return pp.slice(0, 1) + pp.slice(2, 7)
              + pp.slice(8, 13) + pp.slice(14, 19)
@@ -681,12 +615,30 @@ this.Utils = {
    * Get the FxA identity hosts.
    */
   getSyncCredentialsHostsFxA: function() {
+    // This is somewhat expensive and the result static, so we cache the result.
+    if (this._syncCredentialsHostsFxA) {
+      return this._syncCredentialsHostsFxA;
+    }
     let result = new Set();
     // the FxA host
     result.add(FxAccountsCommon.FXA_PWDMGR_HOST);
-    // We used to include the FxA hosts (hence the Set() result) but we now
-    // don't give them special treatment (hence the Set() with exactly 1 item)
-    return result;
+    //
+    // The FxA hosts - these almost certainly all have the same hostname, but
+    // better safe than sorry...
+    for (let prefName of ["identity.fxaccounts.remote.force_auth.uri",
+                          "identity.fxaccounts.remote.signup.uri",
+                          "identity.fxaccounts.remote.signin.uri",
+                          "identity.fxaccounts.settings.uri"]) {
+      let prefVal;
+      try {
+        prefVal = Services.prefs.getCharPref(prefName);
+      } catch (_) {
+        continue;
+      }
+      let uri = Services.io.newURI(prefVal, null, null);
+      result.add(uri.prePath);
+    }
+    return this._syncCredentialsHostsFxA = result;
   },
 
   getDefaultDeviceName() {
@@ -720,32 +672,6 @@ this.Utils = {
       Cc["@mozilla.org/network/protocol;1?name=http"].getService(Ci.nsIHttpProtocolHandler).oscpu;
 
     return Str.sync.get("client.name2", [user, appName, system]);
-  },
-
-  getDeviceName() {
-    const deviceName = Svc.Prefs.get("client.name", "");
-
-    if (deviceName === "") {
-      return this.getDefaultDeviceName();
-    }
-
-    return deviceName;
-  },
-
-  getDeviceType() {
-    return Svc.Prefs.get("client.type", DEVICE_TYPE_DESKTOP);
-  },
-
-  formatTimestamp(date) {
-    // Format timestamp as: "%Y-%m-%d %H:%M:%S"
-    let year = String(date.getFullYear());
-    let month = String(date.getMonth() + 1).padStart(2, "0");
-    let day = String(date.getDate()).padStart(2, "0");
-    let hours = String(date.getHours()).padStart(2, "0");
-    let minutes = String(date.getMinutes()).padStart(2, "0");
-    let seconds = String(date.getSeconds()).padStart(2, "0");
-
-    return `${year}-${month}-${day} ${hours}:${minutes}:${seconds}`;
   }
 };
 
@@ -764,7 +690,7 @@ Svc.Prefs = new Preferences(PREFS_BRANCH);
 Svc.DefaultPrefs = new Preferences({branch: PREFS_BRANCH, defaultBranch: true});
 Svc.Obs = Observers;
 
-var _sessionCID = Services.appinfo.ID == SEAMONKEY_ID ?
+let _sessionCID = Services.appinfo.ID == SEAMONKEY_ID ?
   "@mozilla.org/suite/sessionstore;1" :
   "@mozilla.org/browser/sessionstore;1";