Add m-esr52 at 52.6.0

9 files changed, 5034 insertions, 0 deletions

diff --git a/services/sync/modules/engines/addons.js b/services/sync/modules/engines/addons.js
new file mode 100644
index 000000000..01dab58d1
--- /dev/null
+++ b/services/sync/modules/engines/addons.js
@@ -0,0 +1,813 @@
+/* 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/. */
+
+/*
+ * This file defines the add-on sync functionality.
+ *
+ * There are currently a number of known limitations:
+ *  - We only sync XPI extensions and themes available from addons.mozilla.org.
+ *    We hope to expand support for other add-ons eventually.
+ *  - We only attempt syncing of add-ons between applications of the same type.
+ *    This means add-ons will not synchronize between Firefox desktop and
+ *    Firefox mobile, for example. This is because of significant add-on
+ *    incompatibility between application types.
+ *
+ * Add-on records exist for each known {add-on, app-id} pair in the Sync client
+ * set. Each record has a randomly chosen GUID. The records then contain
+ * basic metadata about the add-on.
+ *
+ * We currently synchronize:
+ *
+ *  - Installations
+ *  - Uninstallations
+ *  - User enabling and disabling
+ *
+ * Synchronization is influenced by the following preferences:
+ *
+ *  - 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;
+
+Cu.import("resource://services-sync/addonutils.js");
+Cu.import("resource://services-sync/addonsreconciler.js");
+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");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "AddonManager",
+                                  "resource://gre/modules/AddonManager.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "AddonRepository",
+                                  "resource://gre/modules/addons/AddonRepository.jsm");
+
+this.EXPORTED_SYMBOLS = ["AddonsEngine", "AddonValidator"];
+
+// 7 days in milliseconds.
+const PRUNE_ADDON_CHANGES_THRESHOLD = 60 * 60 * 24 * 7 * 1000;
+
+/**
+ * AddonRecord represents the state of an add-on in an application.
+ *
+ * Each add-on has its own record for each application ID it is installed
+ * on.
+ *
+ * The ID of add-on records is a randomly-generated GUID. It is random instead
+ * of deterministic so the URIs of the records cannot be guessed and so
+ * compromised server credentials won't result in disclosure of the specific
+ * add-ons present in a Sync account.
+ *
+ * The record contains the following fields:
+ *
+ *  addonID
+ *    ID of the add-on. This correlates to the "id" property on an Addon type.
+ *
+ *  applicationID
+ *    The application ID this record is associated with.
+ *
+ *  enabled
+ *    Boolean stating whether add-on is enabled or disabled by the user.
+ *
+ *  source
+ *    String indicating where an add-on is from. Currently, we only support
+ *    the value "amo" which indicates that the add-on came from the official
+ *    add-ons repository, addons.mozilla.org. In the future, we may support
+ *    installing add-ons from other sources. This provides a future-compatible
+ *    mechanism for clients to only apply records they know how to handle.
+ */
+function AddonRecord(collection, id) {
+  CryptoWrapper.call(this, collection, id);
+}
+AddonRecord.prototype = {
+  __proto__: CryptoWrapper.prototype,
+  _logName: "Record.Addon"
+};
+
+Utils.deferGetSet(AddonRecord, "cleartext", ["addonID",
+                                             "applicationID",
+                                             "enabled",
+                                             "source"]);
+
+/**
+ * The AddonsEngine handles synchronization of add-ons between clients.
+ *
+ * The engine maintains an instance of an AddonsReconciler, which is the entity
+ * maintaining state for add-ons. It provides the history and tracking APIs
+ * that AddonManager doesn't.
+ *
+ * The engine instance overrides a handful of functions on the base class. The
+ * rationale for each is documented by that function.
+ */
+this.AddonsEngine = function AddonsEngine(service) {
+  SyncEngine.call(this, "Addons", service);
+
+  this._reconciler = new AddonsReconciler();
+}
+AddonsEngine.prototype = {
+  __proto__:              SyncEngine.prototype,
+  _storeObj:              AddonsStore,
+  _trackerObj:            AddonsTracker,
+  _recordObj:             AddonRecord,
+  version:                1,
+
+  syncPriority:           5,
+
+  _reconciler:            null,
+
+  /**
+   * Override parent method to find add-ons by their public ID, not Sync GUID.
+   */
+  _findDupe: function _findDupe(item) {
+    let id = item.addonID;
+
+    // The reconciler should have been updated at the top of the sync, so we
+    // can assume it is up to date when this function is called.
+    let addons = this._reconciler.addons;
+    if (!(id in addons)) {
+      return null;
+    }
+
+    let addon = addons[id];
+    if (addon.guid != item.id) {
+      return addon.guid;
+    }
+
+    return null;
+  },
+
+  /**
+   * Override getChangedIDs to pull in tracker changes plus changes from the
+   * reconciler log.
+   */
+  getChangedIDs: function getChangedIDs() {
+    let changes = {};
+    for (let [id, modified] of Object.entries(this._tracker.changedIDs)) {
+      changes[id] = modified;
+    }
+
+    let lastSyncDate = new Date(this.lastSync * 1000);
+
+    // The reconciler should have been refreshed at the beginning of a sync and
+    // 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) {
+      let changeTime = change[0];
+      let id = change[2];
+
+      if (!(id in addons)) {
+        continue;
+      }
+
+      // Keep newest modified time.
+      if (id in changes && changeTime < changes[id]) {
+          continue;
+      }
+
+      if (!this.isAddonSyncable(addons[id])) {
+        continue;
+      }
+
+      this._log.debug("Adding changed add-on from changes log: " + id);
+      let addon = addons[id];
+      changes[addon.guid] = changeTime.getTime() / 1000;
+    }
+
+    return changes;
+  },
+
+  /**
+   * Override start of sync function to refresh reconciler.
+   *
+   * Many functions in this class assume the reconciler is refreshed at the
+   * top of a sync. If this ever changes, those functions should be revisited.
+   *
+   * Technically speaking, we don't need to refresh the reconciler on every
+   * sync since it is installed as an AddonManager listener. However, add-ons
+   * are complicated and we force a full refresh, just in case the listeners
+   * missed something.
+   */
+  _syncStartup: function _syncStartup() {
+    // We refresh state before calling parent because syncStartup in the parent
+    // looks for changed IDs, which is dependent on add-on state being up to
+    // date.
+    this._refreshReconcilerState();
+
+    SyncEngine.prototype._syncStartup.call(this);
+  },
+
+  /**
+   * Override end of sync to perform a little housekeeping on the reconciler.
+   *
+   * We prune changes to prevent the reconciler state from growing without
+   * bound. Even if it grows unbounded, there would have to be many add-on
+   * changes (thousands) for it to slow things down significantly. This is
+   * highly unlikely to occur. Still, we exercise defense just in case.
+   */
+  _syncCleanup: function _syncCleanup() {
+    let ms = 1000 * this.lastSync - PRUNE_ADDON_CHANGES_THRESHOLD;
+    this._reconciler.pruneChangesBeforeDate(new Date(ms));
+
+    SyncEngine.prototype._syncCleanup.call(this);
+  },
+
+  /**
+   * Helper function to ensure reconciler is up to date.
+   *
+   * This will synchronously load the reconciler's state from the file
+   * system (if needed) and refresh the state of the reconciler.
+   */
+  _refreshReconcilerState: function _refreshReconcilerState() {
+    this._log.debug("Refreshing reconciler state");
+    let cb = Async.makeSpinningCallback();
+    this._reconciler.refreshGlobalState(cb);
+    cb.wait();
+  },
+
+  isAddonSyncable(addon, ignoreRepoCheck) {
+    return this._store.isAddonSyncable(addon, ignoreRepoCheck);
+  }
+};
+
+/**
+ * This is the primary interface between Sync and the Addons Manager.
+ *
+ * In addition to the core store APIs, we provide convenience functions to wrap
+ * Add-on Manager APIs with Sync-specific semantics.
+ */
+function AddonsStore(name, engine) {
+  Store.call(this, name, engine);
+}
+AddonsStore.prototype = {
+  __proto__: Store.prototype,
+
+  // Define the add-on types (.type) that we support.
+  _syncableTypes: ["extension", "theme"],
+
+  _extensionsPrefs: new Preferences("extensions."),
+
+  get reconciler() {
+    return this.engine._reconciler;
+  },
+
+  /**
+   * Override applyIncoming to filter out records we can't handle.
+   */
+  applyIncoming: function applyIncoming(record) {
+    // The fields we look at aren't present when the record is deleted.
+    if (!record.deleted) {
+      // Ignore records not belonging to our application ID because that is the
+      // current policy.
+      if (record.applicationID != Services.appinfo.ID) {
+        this._log.info("Ignoring incoming record from other App ID: " +
+                        record.id);
+        return;
+      }
+
+      // Ignore records that aren't from the official add-on repository, as that
+      // is our current policy.
+      if (record.source != "amo") {
+        this._log.info("Ignoring unknown add-on source (" + record.source + ")" +
+                       " for " + record.id);
+        return;
+      }
+    }
+
+    // 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);
+  },
+
+
+  /**
+   * Provides core Store API to create/install an add-on from a record.
+   */
+  create: function create(record) {
+    let cb = Async.makeSpinningCallback();
+    AddonUtils.installAddons([{
+      id:               record.addonID,
+      syncGUID:         record.id,
+      enabled:          record.enabled,
+      requireSecureURI: this._extensionsPrefs.get("install.requireSecureOrigin", true),
+    }], 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) {
+      if (a.id == record.addonID) {
+        addon = a;
+        break;
+      }
+    }
+
+    // This should never happen, but is present as a fail-safe.
+    if (!addon) {
+      throw new Error("Add-on not found after install: " + record.addonID);
+    }
+
+    this._log.info("Add-on installed: " + record.addonID);
+  },
+
+  /**
+   * Provides core Store API to remove/uninstall an add-on from a record.
+   */
+  remove: function remove(record) {
+    // If this is called, the payload is empty, so we have to find by GUID.
+    let addon = this.getAddonByGUID(record.id);
+    if (!addon) {
+      // We don't throw because if the add-on could not be found then we assume
+      // it has already been uninstalled and there is nothing for this function
+      // to do.
+      return;
+    }
+
+    this._log.info("Uninstalling add-on: " + addon.id);
+    let cb = Async.makeSpinningCallback();
+    AddonUtils.uninstallAddon(addon, cb);
+    cb.wait();
+  },
+
+  /**
+   * Provides core Store API to update an add-on from a record.
+   */
+  update: function update(record) {
+    let addon = this.getAddonByID(record.addonID);
+
+    // update() is called if !this.itemExists. And, since itemExists consults
+    // the reconciler only, we need to take care of some corner cases.
+    //
+    // First, the reconciler could know about an add-on that was uninstalled
+    // and no longer present in the add-ons manager.
+    if (!addon) {
+      this.create(record);
+      return;
+    }
+
+    // It's also possible that the add-on is non-restartless and has pending
+    // install/uninstall activity.
+    //
+    // We wouldn't get here if the incoming record was for a deletion. So,
+    // check for pending uninstall and cancel if necessary.
+    if (addon.pendingOperations & AddonManager.PENDING_UNINSTALL) {
+      addon.cancelUninstall();
+
+      // We continue with processing because there could be state or ID change.
+    }
+
+    let cb = Async.makeSpinningCallback();
+    this.updateUserDisabled(addon, !record.enabled, cb);
+    cb.wait();
+  },
+
+  /**
+   * Provide core Store API to determine if a record exists.
+   */
+  itemExists: function itemExists(guid) {
+    let addon = this.reconciler.getAddonStateFromSyncGUID(guid);
+
+    return !!addon;
+  },
+
+  /**
+   * Create an add-on record from its GUID.
+   *
+   * @param guid
+   *        Add-on GUID (from extensions DB)
+   * @param collection
+   *        Collection to add record to.
+   *
+   * @return AddonRecord instance
+   */
+  createRecord: function createRecord(guid, collection) {
+    let record = new AddonRecord(collection, guid);
+    record.applicationID = Services.appinfo.ID;
+
+    let addon = this.reconciler.getAddonStateFromSyncGUID(guid);
+
+    // If we don't know about this GUID or if it has been uninstalled, we mark
+    // the record as deleted.
+    if (!addon || !addon.installed) {
+      record.deleted = true;
+      return record;
+    }
+
+    record.modified = addon.modified.getTime() / 1000;
+
+    record.addonID = addon.id;
+    record.enabled = addon.enabled;
+
+    // This needs to be dynamic when add-ons don't come from AddonRepository.
+    record.source = "amo";
+
+    return record;
+  },
+
+  /**
+   * Changes the id of an add-on.
+   *
+   * This implements a core API of the store.
+   */
+  changeItemID: function changeItemID(oldID, newID) {
+    // We always update the GUID in the reconciler because it will be
+    // referenced later in the sync process.
+    let state = this.reconciler.getAddonStateFromSyncGUID(oldID);
+    if (state) {
+      state.guid = newID;
+      let cb = Async.makeSpinningCallback();
+      this.reconciler.saveState(null, cb);
+      cb.wait();
+    }
+
+    let addon = this.getAddonByGUID(oldID);
+    if (!addon) {
+      this._log.debug("Cannot change item ID (" + oldID + ") in Add-on " +
+                      "Manager because old add-on not present: " + oldID);
+      return;
+    }
+
+    addon.syncGUID = newID;
+  },
+
+  /**
+   * Obtain the set of all syncable add-on Sync GUIDs.
+   *
+   * This implements a core Store API.
+   */
+  getAllIDs: function getAllIDs() {
+    let ids = {};
+
+    let addons = this.reconciler.addons;
+    for (let id in addons) {
+      let addon = addons[id];
+      if (this.isAddonSyncable(addon)) {
+        ids[addon.guid] = true;
+      }
+    }
+
+    return ids;
+  },
+
+  /**
+   * Wipe engine data.
+   *
+   * This uninstalls all syncable addons from the application. In case of
+   * error, it logs the error and keeps trying with other add-ons.
+   */
+  wipe: function wipe() {
+    this._log.info("Processing wipe.");
+
+    this.engine._refreshReconcilerState();
+
+    // We only wipe syncable add-ons. Wipe is a Sync feature not a security
+    // feature.
+    for (let guid in this.getAllIDs()) {
+      let addon = this.getAddonByGUID(guid);
+      if (!addon) {
+        this._log.debug("Ignoring add-on because it couldn't be obtained: " +
+                        guid);
+        continue;
+      }
+
+      this._log.info("Uninstalling add-on as part of wipe: " + addon.id);
+      Utils.catch.call(this, () => addon.uninstall())();
+    }
+  },
+
+  /***************************************************************************
+   * Functions below are unique to this store and not part of the Store API  *
+   ***************************************************************************/
+
+  /**
+   * Synchronously obtain an add-on from its public ID.
+   *
+   * @param id
+   *        Add-on ID
+   * @return Addon or undefined if not found
+   */
+  getAddonByID: function getAddonByID(id) {
+    let cb = Async.makeSyncCallback();
+    AddonManager.getAddonByID(id, cb);
+    return Async.waitForSyncCallback(cb);
+  },
+
+  /**
+   * Synchronously obtain an add-on from its Sync GUID.
+   *
+   * @param  guid
+   *         Add-on Sync GUID
+   * @return DBAddonInternal or null
+   */
+  getAddonByGUID: function getAddonByGUID(guid) {
+    let cb = Async.makeSyncCallback();
+    AddonManager.getAddonBySyncGUID(guid, cb);
+    return Async.waitForSyncCallback(cb);
+  },
+
+  /**
+   * Determines whether an add-on is suitable for Sync.
+   *
+   * @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) {
+    // 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
+
+    // We could represent the test as a complex boolean expression. We go the
+    // verbose route so the failure reason is logged.
+    if (!addon) {
+      this._log.debug("Null object passed to isAddonSyncable.");
+      return false;
+    }
+
+    if (this._syncableTypes.indexOf(addon.type) == -1) {
+      this._log.debug(addon.id + " not syncable: type not in whitelist: " +
+                      addon.type);
+      return false;
+    }
+
+    if (!(addon.scope & AddonManager.SCOPE_PROFILE)) {
+      this._log.debug(addon.id + " not syncable: not installed in profile.");
+      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.
+    // TODO Address the edge case and come up with more robust heuristics.
+    if (addon.foreignInstall) {
+      this._log.debug(addon.id + " not syncable: is foreign install.");
+      return false;
+    }
+
+    // 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) {
+      return true;
+    }
+
+    let cb = Async.makeSyncCallback();
+    AddonRepository.getCachedAddonByID(addon.id, cb);
+    let result = Async.waitForSyncCallback(cb);
+
+    if (!result) {
+      this._log.debug(addon.id + " not syncable: add-on not found in add-on " +
+                      "repository.");
+      return false;
+    }
+
+    return this.isSourceURITrusted(result.sourceURI);
+  },
+
+  /**
+   * Determine whether an add-on's sourceURI field is trusted and the add-on
+   * can be installed.
+   *
+   * This function should only ever be called from isAddonSyncable(). It is
+   * exposed as a separate function to make testing easier.
+   *
+   * @param  uri
+   *         nsIURI instance to validate
+   * @return bool
+   */
+  isSourceURITrusted: function isSourceURITrusted(uri) {
+    // For security reasons, we currently limit synced add-ons to those
+    // installed from trusted hostname(s). We additionally require TLS with
+    // the add-ons site to help prevent forgeries.
+    let trustedHostnames = Svc.Prefs.get("addons.trustedSourceHostnames", "")
+                           .split(",");
+
+    if (!uri) {
+      this._log.debug("Undefined argument to isSourceURITrusted().");
+      return false;
+    }
+
+    // Scheme is validated before the hostname because uri.host may not be
+    // populated for certain schemes. It appears to always be populated for
+    // https, so we avoid the potential NS_ERROR_FAILURE on field access.
+    if (uri.scheme != "https") {
+      this._log.debug("Source URI not HTTPS: " + uri.spec);
+      return false;
+    }
+
+    if (trustedHostnames.indexOf(uri.host) == -1) {
+      this._log.debug("Source hostname not trusted: " + uri.host);
+      return false;
+    }
+
+    return true;
+  },
+
+  /**
+   * Update the userDisabled flag on an add-on.
+   *
+   * This will enable or disable an add-on and call the supplied callback when
+   * the action is complete. If no action is needed, the callback gets called
+   * immediately.
+   *
+   * @param addon
+   *        Addon instance to manipulate.
+   * @param value
+   *        Boolean to which to set userDisabled on the passed Addon.
+   * @param callback
+   *        Function to be called when action is complete. Will receive 2
+   *        arguments, a truthy value that signifies error, and the Addon
+   *        instance passed to this function.
+   */
+  updateUserDisabled: function updateUserDisabled(addon, value, callback) {
+    if (addon.userDisabled == value) {
+      callback(null, addon);
+      return;
+    }
+
+    // A pref allows changes to the enabled flag to be ignored.
+    if (Svc.Prefs.get("addons.ignoreUserEnabledChanges", false)) {
+      this._log.info("Ignoring enabled state change due to preference: " +
+                     addon.id);
+      callback(null, addon);
+      return;
+    }
+
+    AddonUtils.updateUserDisabled(addon, value, callback);
+  },
+};
+
+/**
+ * The add-ons tracker keeps track of real-time changes to add-ons.
+ *
+ * It hooks up to the reconciler and receives notifications directly from it.
+ */
+function AddonsTracker(name, engine) {
+  Tracker.call(this, name, engine);
+}
+AddonsTracker.prototype = {
+  __proto__: Tracker.prototype,
+
+  get reconciler() {
+    return this.engine._reconciler;
+  },
+
+  get store() {
+    return this.engine._store;
+  },
+
+  /**
+   * This callback is executed whenever the AddonsReconciler sends out a change
+   * notification. See AddonsReconciler.addChangeListener().
+   */
+  changeListener: function changeHandler(date, change, addon) {
+    this._log.debug("changeListener invoked: " + change + " " + addon.id);
+    // Ignore changes that occur during sync.
+    if (this.ignoreAll) {
+      return;
+    }
+
+    if (!this.store.isAddonSyncable(addon)) {
+      this._log.debug("Ignoring change because add-on isn't syncable: " +
+                      addon.id);
+      return;
+    }
+
+    this.addChangedID(addon.guid, date.getTime() / 1000);
+    this.score += SCORE_INCREMENT_XLARGE;
+  },
+
+  startTracking: function() {
+    if (this.engine.enabled) {
+      this.reconciler.startListening();
+    }
+
+    this.reconciler.addChangeListener(this);
+  },
+
+  stopTracking: function() {
+    this.reconciler.removeChangeListener(this);
+    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
new file mode 100644
index 000000000..76a198a8b
--- /dev/null
+++ b/services/sync/modules/engines/bookmarks.js
@@ -0,0 +1,1378 @@
+/* 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/. */
+
+this.EXPORTED_SYMBOLS = ['BookmarksEngine', "PlacesItem", "Bookmark",
+                         "BookmarkFolder", "BookmarkQuery",
+                         "Livemark", "BookmarkSeparator"];
+
+var Cc = Components.classes;
+var Ci = Components.interfaces;
+var 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");
+Cu.import("resource://services-sync/engines.js");
+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,
+                        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);
+  this.type = type || "item";
+}
+PlacesItem.prototype = {
+  decrypt: function PlacesItem_decrypt(keyBundle) {
+    // Do the normal CryptoWrapper decrypt, but change types before returning
+    let clear = CryptoWrapper.prototype.decrypt.call(this, keyBundle);
+
+    // Convert the abstract places item to the actual object type
+    if (!this.deleted)
+      this.__proto__ = this.getTypeObject(this.type).prototype;
+
+    return clear;
+  },
+
+  getTypeObject: function PlacesItem_getTypeObject(type) {
+    let recordObj = getTypeObject(type);
+    if (!recordObj) {
+      throw new Error("Unknown places item object type: " + type);
+    }
+    return recordObj;
+  },
+
+  __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,
+                  "cleartext",
+                  ["hasDupe", "parentid", "parentName", "type"]);
+
+this.Bookmark = function Bookmark(collection, id, type) {
+  PlacesItem.call(this, collection, id, type || "bookmark");
+}
+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,
+                  "cleartext",
+                  ["title", "bmkUri", "description",
+                   "loadInSidebar", "tags", "keyword"]);
+
+this.BookmarkQuery = function BookmarkQuery(collection, id) {
+  Bookmark.call(this, collection, id, "query");
+}
+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,
+                  "cleartext",
+                  ["folderName", "queryId"]);
+
+this.BookmarkFolder = function BookmarkFolder(collection, id, type) {
+  PlacesItem.call(this, collection, id, type || "folder");
+}
+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",
+                                                "children"]);
+
+this.Livemark = function Livemark(collection, id) {
+  BookmarkFolder.call(this, collection, id, "livemark");
+}
+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"]);
+
+this.BookmarkSeparator = function BookmarkSeparator(collection, id) {
+  PlacesItem.call(this, collection, id, "separator");
+}
+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");
+
+this.BookmarksEngine = function BookmarksEngine(service) {
+  SyncEngine.call(this, "Bookmarks", service);
+}
+BookmarksEngine.prototype = {
+  __proto__: SyncEngine.prototype,
+  _recordObj: PlacesItem,
+  _storeObj: BookmarksStore,
+  _trackerObj: BookmarksTracker,
+  version: 2,
+  _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];
+        }
+        if (tree.children) {
+          for (let child of tree.children) {
+            store._sleep(0); // avoid jank while looping.
+            yield* walkBookmarksTree(child, tree);
+          }
+        }
+      }
+    }
+
+    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);
+      }
+    }
+
+    let rootsToWalk = getChangeRootIds();
+
+    for (let [node, parent] of walkBookmarksRoots(tree, rootsToWalk)) {
+      let {guid, id, type: placeType} = node;
+      guid = PlacesSyncUtils.bookmarks.guidToSyncId(guid);
+      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 || "");
+          }
+          break;
+        case PlacesUtils.TYPE_X_MOZ_PLACE_CONTAINER:
+          // Folder
+          key = "f" + (node.title || "");
+          break;
+        case PlacesUtils.TYPE_X_MOZ_PLACE_SEPARATOR:
+          // Separator
+          key = "s" + node.index;
+          break;
+        default:
+          this._log.error("Unknown place type: '"+placeType+"'");
+          continue;
+      }
+
+      let parentName = parent.title || "";
+      if (guidMap[parentName] == null)
+        guidMap[parentName] = {};
+
+      // If the entry already exists, remember that there are explicit dupes.
+      let entry = new String(guid);
+      entry.hasDupe = guidMap[parentName][key] != null;
+
+      // Remember this item's GUID for its parent-name/key pair.
+      guidMap[parentName][key] = entry;
+      this._log.trace("Mapped: " + [parentName, key, entry, entry.hasDupe]);
+    }
+
+    return guidMap;
+  },
+
+  // Helper function to get a dupe GUID for an item.
+  _mapDupe: function _mapDupe(item) {
+    // Figure out if we have something to key with.
+    let key;
+    let altKey;
+    switch (item.type) {
+      case "query":
+        // Prior to Bug 610501, records didn't carry their Smart Bookmark
+        // anno, so we won't be able to dupe them correctly. This altKey
+        // hack should get them to dupe correctly.
+        if (item.queryId) {
+          key = "q" + item.queryId;
+          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 || "");
+        break;
+      case "folder":
+      case "livemark":
+        key = "f" + (item.title || "");
+        break;
+      case "separator":
+        key = "s" + item.pos;
+        break;
+      default:
+        return;
+    }
+
+    // Figure out if we have a map to use!
+    // This will throw in some circumstances. That's fine.
+    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];
+
+    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) {
+        this._log.trace("Mapped dupe using altKey " + altKey + ": " + dupe);
+        return dupe;
+      }
+    }
+
+    this._log.trace("No dupe found for key " + key + "/" + altKey + ".");
+    return undefined;
+  },
+
+  _syncStartup: function _syncStart() {
+    SyncEngine.prototype._syncStartup.call(this);
+
+    let cb = Async.makeSpinningCallback();
+    Task.spawn(function* () {
+      // For first-syncs, make a backup for the user to restore
+      if (this.lastSync == 0) {
+        this._log.debug("Bookmarks backup starting.");
+        yield PlacesBackups.create(null, true);
+        this._log.debug("Bookmarks backup done.");
+      }
+    }.bind(this)).then(
+      cb, ex => {
+        // 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);
+        cb();
+      }
+    );
+
+    cb.wait();
+
+    this.__defineGetter__("_guidMap", function() {
+      // Create a mapping of folder titles and separator positions to GUID.
+      // We do this lazily so that we don't do any work unless we reconcile
+      // incoming items.
+      let guidMap;
+      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);
+        throw {code: Engine.prototype.eEngineAbortApplyIncoming,
+               cause: ex};
+      }
+      delete this._guidMap;
+      return this._guidMap = guidMap;
+    });
+
+    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;
+      }
+    }
+  },
+
+  _syncFinish: function _syncFinish() {
+    SyncEngine.prototype._syncFinish.call(this);
+    this._tracker._ensureMobileQuery();
+  },
+
+  _syncCleanup: function _syncCleanup() {
+    SyncEngine.prototype._syncCleanup.call(this);
+    delete this._guidMap;
+  },
+
+  _createRecord: function _createRecord(id) {
+    // Create the record as usual, but mark it as having dupes if necessary.
+    let record = SyncEngine.prototype._createRecord.call(this, id);
+    let entry = this._mapDupe(record);
+    if (entry != null && entry.hasDupe) {
+      record.hasDupe = true;
+    }
+    return record;
+  },
+
+  _findDupe: function _findDupe(item) {
+    this._log.trace("Finding dupe for " + item.id +
+                    " (already duped: " + item.hasDupe + ").");
+
+    // Don't bother finding a dupe if the incoming item has duplicates.
+    if (item.hasDupe) {
+      this._log.trace(item.id + " already a dupe: not finding one.");
+      return;
+    }
+    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();
+  }
+};
+
+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];
+      stmt.finalize();
+    }
+    this._stmts = {};
+  }, this);
+}
+BookmarksStore.prototype = {
+  __proto__: Store.prototype,
+
+  itemExists: function BStore_itemExists(id) {
+    return this.idForGUID(id) > 0;
+  },
+
+  applyIncoming: function BStore_applyIncoming(record) {
+    this._log.debug("Applying record " + record.id);
+    let isSpecial = PlacesSyncUtils.bookmarks.ROOTS.includes(record.id);
+
+    if (record.deleted) {
+      if (isSpecial) {
+        this._log.warn("Ignoring deletion for special record " + record.id);
+        return;
+      }
+
+      // Don't bother with pre and post-processing for deletions.
+      Store.prototype.applyIncoming.call(this, record);
+      return;
+    }
+
+    // For special folders we're only interested in child ordering.
+    if (isSpecial && record.children) {
+      this._log.debug("Processing special node: " + record.id);
+      // Reorder children later
+      this._childrenToOrder[record.id] = record.children;
+      return;
+    }
+
+    // Skip malformed records. (Bug 806460.)
+    if (record.type == "query" &&
+        !record.bmkUri) {
+      this._log.warn("Skipping malformed query bookmark: " + record.id);
+      return;
+    }
+
+    // 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);
+
+    // 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;
+    }
+  },
+
+  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 ${
+        item.parentSyncId}`, item);
+    }
+  },
+
+  remove: function BStore_remove(record) {
+    if (PlacesSyncUtils.bookmarks.isRootSyncID(record.id)) {
+      this._log.warn("Refusing to remove special folder " + record.id);
+      return;
+    }
+    let recordKind = Async.promiseSpinningly(
+      PlacesSyncUtils.bookmarks.getKindForSyncId(record.id));
+    let isFolder = recordKind === PlacesSyncUtils.bookmarks.KINDS.FOLDER;
+    this._log.trace(`Buffering removal of item "${record.id}" of type "${recordKind}".`);
+    if (isFolder) {
+      this._foldersToDelete.add(record.id);
+    } else {
+      this._atomsToDelete.add(record.id);
+    }
+  },
+
+  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);
+    }
+  },
+
+  _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);
+    }
+  }),
+
+  _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))));
+
+      this._log.trace(`Moving ${childSyncIds.length} children of "${syncId}" to ` +
+                      `grandparent "${grandparentSyncId}" before deletion.`);
+
+      // Move children out of the parent and into the grandparent
+      yield Promise.all(childSyncIds.map(child => PlacesSyncUtils.bookmarks.update({
+        syncId: child,
+        parentSyncId: grandparentSyncId
+      })));
+
+      // 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);
+      }
+
+      // 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);
+        }
+      }
+    }
+    return [...needUpdate];
+  }),
+
+  changeItemID: function BStore_changeItemID(oldID, newID) {
+    this._log.debug("Changing GUID " + oldID + " to " + newID);
+
+    Async.promiseSpinningly(PlacesSyncUtils.bookmarks.changeGuid(oldID, newID));
+  },
+
+  // 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);
+      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 record = new recordObj(collection, id);
+    record.fromSyncBookmark(item);
+
+    record.sortindex = this._calculateIndex(record);
+
+    return record;
+  },
+
+  _stmts: {},
+  _getStmt: function(query) {
+    if (query in this._stmts) {
+      return this._stmts[query];
+    }
+
+    this._log.trace("Creating SQL statement: " + query);
+    let db = PlacesUtils.history.QueryInterface(Ci.nsPIPlacesDatabase)
+                        .DBConnection;
+    return this._stmts[query] = db.createAsyncStatement(query);
+  },
+
+  get _frecencyStm() {
+    return this._getStmt(
+        "SELECT frecency " +
+        "FROM moz_places " +
+        "WHERE url_hash = hash(:url) AND url = :url " +
+        "LIMIT 1");
+  },
+  _frecencyCols: ["frecency"],
+
+  GUIDForId: function GUIDForId(id) {
+    let guid = Async.promiseSpinningly(PlacesUtils.promiseItemGuid(id));
+    return PlacesSyncUtils.bookmarks.guidToSyncId(guid);
+  },
+
+  idForGUID: function idForGUID(guid) {
+    // guid might be a String object rather than a string.
+    guid = PlacesSyncUtils.bookmarks.syncIdToGuid(guid.toString());
+
+    return Async.promiseSpinningly(PlacesUtils.promiseItemId(guid).catch(
+      ex => -1));
+  },
+
+  _calculateIndex: function _calculateIndex(record) {
+    // Ensure folders have a very high sort index so they're not synced last.
+    if (record.type == "folder")
+      return FOLDER_SORTINDEX;
+
+    // For anything directly under the toolbar, give it a boost of more than an
+    // unvisited bookmark
+    let index = 0;
+    if (record.parentid == "toolbar")
+      index += 150;
+
+    // Add in the bookmark's frecency if we have something.
+    if (record.bmkUri != null) {
+      this._frecencyStm.params.url = record.bmkUri;
+      let result = Async.querySpinningly(this._frecencyStm, this._frecencyCols);
+      if (result.length)
+        index += result[0].frecency;
+    }
+
+    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 };
+    }
+
+    return items;
+  },
+
+  wipe: function BStore_wipe() {
+    this.clearPendingDeletions();
+    Async.promiseSpinningly(Task.spawn(function* () {
+      // Save a backup before clearing out all bookmarks.
+      yield PlacesBackups.create(null, true);
+      yield PlacesUtils.bookmarks.eraseEverything({
+        source: SOURCE_SYNC,
+      });
+    }));
+  }
+};
+
+function BookmarksTracker(name, engine) {
+  this._batchDepth = 0;
+  this._batchSawScoreIncrement = false;
+  Tracker.call(this, name, engine);
+
+  Svc.Obs.add("places-shutdown", this);
+}
+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);
+    Svc.Obs.add("bookmarks-restore-success", this);
+    Svc.Obs.add("bookmarks-restore-failed", this);
+  },
+
+  stopTracking: function() {
+    PlacesUtils.bookmarks.removeObserver(this);
+    Svc.Obs.remove("bookmarks-restore-begin", this);
+    Svc.Obs.remove("bookmarks-restore-success", this);
+    Svc.Obs.remove("bookmarks-restore-failed", this);
+  },
+
+  observe: function observe(subject, topic, data) {
+    Tracker.prototype.observe.call(this, subject, topic, data);
+
+    switch (topic) {
+      case "bookmarks-restore-begin":
+        this._log.debug("Ignoring changes from importing bookmarks.");
+        break;
+      case "bookmarks-restore-success":
+        this._log.debug("Tracking all items on successful import.");
+
+        this._log.debug("Restore succeeded: wiping server and other clients.");
+        this.engine.service.resetClient([this.name]);
+        this.engine.service.wipeServer([this.name]);
+        this.engine.service.clientsEngine.sendCommand("wipeEngine", [this.name]);
+        break;
+      case "bookmarks-restore-failed":
+        this._log.debug("Tracking all items on failed import.");
+        break;
+    }
+  },
+
+  QueryInterface: XPCOMUtils.generateQI([
+    Ci.nsINavBookmarkObserver,
+    Ci.nsINavBookmarkObserver_MOZILLA_1_9_1_ADDITIONS,
+    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.
+   */
+  _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)) {
+      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) */
+  _upScore: function BMT__upScore() {
+    if (this._batchDepth == 0) {
+      this.score += SCORE_INCREMENT_XLARGE;
+    } else {
+      this._batchSawScoreIncrement = true;
+    }
+  },
+
+  onItemAdded: function BMT_onItemAdded(itemId, folder, index,
+                                        itemType, uri, title, dateAdded,
+                                        guid, parentGuid, source) {
+    if (IGNORED_SOURCES.includes(source)) {
+      return;
+    }
+
+    this._log.trace("onItemAdded: " + itemId);
+    this._add(itemId, guid);
+    this._add(folder, parentGuid);
+  },
+
+  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) {
+      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(parentId, parentGuid);
+  },
+
+  _ensureMobileQuery: function _ensureMobileQuery() {
+    let find = val =>
+      PlacesUtils.annotations.getItemsWithAnnotation(ORGANIZERQUERY_ANNO, {}).filter(
+        id => PlacesUtils.annotations.getItemAnnotation(id, ORGANIZERQUERY_ANNO) == val
+      );
+
+    // Don't continue if the Library isn't ready
+    let all = find(ALLBOOKMARKS_ANNO);
+    if (all.length == 0)
+      return;
+
+    let mobile = find(MOBILE_ANNO);
+    let queryURI = Utils.makeURI("place:folder=" + PlacesUtils.mobileFolderId);
+    let title = PlacesBundle.GetStringFromName("MobileBookmarksFolderTitle");
+
+    // Don't add OR remove the mobile bookmarks if there's nothing.
+    if (PlacesUtils.bookmarks.getIdForItemAt(PlacesUtils.mobileFolderId, 0) == -1) {
+      if (mobile.length != 0)
+        PlacesUtils.bookmarks.removeItem(mobile[0], SOURCE_SYNC);
+    }
+    // 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);
+      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);
+    }
+    // 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);
+      }
+    }
+  },
+
+  // This method is oddly structured, but the idea is to return as quickly as
+  // possible -- this handler gets called *every time* a bookmark changes, for
+  // *each change*.
+  onItemChanged: function BMT_onItemChanged(itemId, property, isAnno, value,
+                                            lastModified, itemType, parentId,
+                                            guid, parentGuid, oldValue,
+                                            source) {
+    if (IGNORED_SOURCES.includes(source)) {
+      return;
+    }
+
+    if (isAnno && (ANNOS_TO_TRACK.indexOf(property) == -1))
+      // Ignore annotations except for the ones that we sync.
+      return;
+
+    // Ignore favicon changes to avoid unnecessary churn.
+    if (property == "favicon")
+      return;
+
+    this._log.trace("onItemChanged: " + itemId +
+                    (", " + property + (isAnno? " (anno)" : "")) +
+                    (value ? (" = \"" + value + "\"") : ""));
+    this._add(itemId, guid);
+  },
+
+  onItemMoved: function BMT_onItemMoved(itemId, oldParent, oldIndex,
+                                        newParent, newIndex, itemType,
+                                        guid, oldParentGuid, newParentGuid,
+                                        source) {
+    if (IGNORED_SOURCES.includes(source)) {
+      return;
+    }
+
+    this._log.trace("onItemMoved: " + itemId);
+    this._add(oldParent, oldParentGuid);
+    if (oldParent != newParent) {
+      this._add(itemId, guid);
+      this._add(newParent, newParentGuid);
+    }
+
+    // Remove any position annotations now that the user moved the item
+    PlacesUtils.annotations.removeItemAnnotation(itemId,
+      PlacesSyncUtils.bookmarks.SYNC_PARENT_ANNO, SOURCE_SYNC);
+  },
+
+  onBeginUpdateBatch: function () {
+    ++this._batchDepth;
+  },
+  onEndUpdateBatch: function () {
+    if (--this._batchDepth === 0 && this._batchSawScoreIncrement) {
+      this.score += SCORE_INCREMENT_XLARGE;
+      this._batchSawScoreIncrement = false;
+    }
+  },
+  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
new file mode 100644
index 000000000..3dd679570
--- /dev/null
+++ b/services/sync/modules/engines/clients.js
@@ -0,0 +1,782 @@
+/* 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/. */
+
+/**
+ * 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;
+
+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);
+}
+ClientsRec.prototype = {
+  __proto__: CryptoWrapper.prototype,
+  _logName: "Sync.Record.Clients",
+  ttl: CLIENTS_TTL
+};
+
+Utils.deferGetSet(ClientsRec,
+                  "cleartext",
+                  ["name", "type", "commands",
+                   "version", "protocols",
+                   "formfactor", "os", "appPackage", "application", "device",
+                   "fxaDeviceId"]);
+
+
+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();
+}
+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 lastRecordUpload() {
+    return Svc.Prefs.get(this.name + ".lastRecordUpload", 0);
+  },
+  set lastRecordUpload(value) {
+    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,
+      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++;
+      }
+    }
+
+    return stats;
+  },
+
+  /**
+   * Obtain information about device types.
+   *
+   * Returns a Map of device types to integer counts.
+   */
+  get deviceTypes() {
+    let counts = new Map();
+
+    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.
+      }
+      let type = record.type;
+      if (!counts.has(type)) {
+        counts.set(type, 0);
+      }
+
+      counts.set(type, counts.get(type) + 1);
+    }
+
+    return counts;
+  },
+
+  get localID() {
+    // Generate a random GUID id we don't have one
+    let localID = Svc.Prefs.get("client.GUID", "");
+    return localID == "" ? this.localID = Utils.makeGUID() : localID;
+  },
+  set localID(value) {
+    Svc.Prefs.set("client.GUID", value);
+  },
+
+  get brandName() {
+    let brand = new StringBundle("chrome://branding/locale/brand.properties");
+    return brand.get("brandShortName");
+  },
+
+  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);
+    });
+  },
+
+  get localType() {
+    return Utils.getDeviceType();
+  },
+  set localType(value) {
+    Svc.Prefs.set("client.type", 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;
+  },
+
+  isMobile: function isMobile(id) {
+    if (this._store._remoteClients[id])
+      return this._store._remoteClients[id].type == DEVICE_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) {
+      this._tracker.addChangedID(this.localID);
+      this.lastRecordUpload = Date.now() / 1000;
+    }
+    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;
+  },
+
+  // Treat reset the same as wiping for locally cached clients
+  _resetClient() {
+    this._wipeClient();
+  },
+
+  _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() {
+    let res = this.service.resource(this.engineURL + "/" + this.localID);
+    res.delete();
+  },
+
+  // Override the default behavior to delete bad records from the server.
+  handleHMACMismatch: function handleHMACMismatch(item, mayRetry) {
+    this._log.debug("Handling HMAC mismatch for " + item.id);
+
+    let base = SyncEngine.prototype.handleHMACMismatch.call(this, item, mayRetry);
+    if (base != SyncEngine.kRecoveryStrategy.error)
+      return base;
+
+    // It's a bad client record. Save it to be deleted at the end of the sync.
+    this._log.debug("Bad client record detected. Scheduling for deletion.");
+    this._deleteId(item.id);
+
+    // Neither try again nor error; we're going to delete it.
+    return SyncEngine.kRecoveryStrategy.ignore;
+  },
+
+  /**
+   * A hash of valid commands that the client knows about. The key is a command
+   * and the value is a hash containing information about the command such as
+   * number of arguments and description.
+   */
+  _commands: {
+    resetAll:    { args: 0, desc: "Clear temporary local data for all engines" },
+    resetEngine: { args: 1, desc: "Clear temporary local data for engine" },
+    wipeAll:     { args: 0, desc: "Delete all client data for all engines" },
+    wipeEngine:  { args: 1, desc: "Delete all client data for engine" },
+    logout:      { args: 0, desc: "Log out client" },
+    displayURI:  { args: 3, desc: "Instruct a client to display a URI" },
+  },
+
+  /**
+   * Sends a command+args pair to a specific client.
+   *
+   * @param command Command string
+   * @param args Array of arguments/data for command
+   * @param clientId Client to send command to
+   */
+  _sendCommandToClient: function sendCommandToClient(command, args, clientId) {
+    this._log.trace("Sending " + command + " to " + clientId);
+
+    let client = this._store._remoteClients[clientId];
+    if (!client) {
+      throw new Error("Unknown remote client ID: '" + clientId + "'.");
+    }
+    if (client.stale) {
+      throw new Error("Stale remote client ID: '" + clientId + "'.");
+    }
+
+    let action = {
+      command: command,
+      args: args,
+    };
+
+    this._log.trace("Client " + clientId + " got a new action: " + [command, args]);
+    this._addClientCommand(clientId, action);
+    this._tracker.addChangedID(clientId);
+  },
+
+  /**
+   * Check if the local client has any remote commands and perform them.
+   *
+   * @return false to abort sync
+   */
+  processIncomingCommands: function processIncomingCommands() {
+    return this._notify("clients:process-commands", "", function() {
+      if (!this.localCommands) {
+        return true;
+      }
+
+      const clearedCommands = this._readCommands()[this.localID];
+      const commands = this.localCommands.filter(command => !hasDupeCommand(clearedCommands, command));
+
+      let URIsToDisplay = [];
+      // Process each command in order.
+      for (let rawCommand of commands) {
+        let {command, args} = rawCommand;
+        this._log.debug("Processing command: " + command + "(" + args + ")");
+
+        let engines = [args[0]];
+        switch (command) {
+          case "resetAll":
+            engines = null;
+            // Fallthrough
+          case "resetEngine":
+            this.service.resetClient(engines);
+            break;
+          case "wipeAll":
+            engines = null;
+            // Fallthrough
+          case "wipeEngine":
+            this.service.wipeClient(engines);
+            break;
+          case "logout":
+            this.service.logout();
+            return false;
+          case "displayURI":
+            let [uri, clientId, title] = args;
+            URIsToDisplay.push({ uri, clientId, title });
+            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;
+    })();
+  },
+
+  /**
+   * Validates and sends a command to a client or all clients.
+   *
+   * Calling this does not actually sync the command data to the server. If the
+   * client already has the command/args pair, it won't receive a duplicate
+   * command.
+   *
+   * @param command
+   *        Command to invoke on remote clients
+   * @param args
+   *        Array of arguments to give to the command
+   * @param clientId
+   *        Client ID to send command to. If undefined, send to all remote
+   *        clients.
+   */
+  sendCommand: function sendCommand(command, args, clientId) {
+    let commandData = this._commands[command];
+    // Don't send commands that we don't know about.
+    if (!commandData) {
+      this._log.error("Unknown command to send: " + command);
+      return;
+    }
+    // Don't send a command with the wrong number of arguments.
+    else if (!args || args.length != commandData.args) {
+      this._log.error("Expected " + commandData.args + " args for '" +
+                      command + "', but got " + args);
+      return;
+    }
+
+    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);
+        }
+      }
+    }
+  },
+
+  /**
+   * Send a URI to another client for display.
+   *
+   * A side effect is the score is increased dramatically to incur an
+   * immediate sync.
+   *
+   * If an unknown client ID is specified, sendCommand() will throw an
+   * Error object.
+   *
+   * @param uri
+   *        URI (as a string) to send and display on the remote client
+   * @param clientId
+   *        ID of client to send the command to. If not defined, will be sent
+   *        to all remote clients.
+   * @param title
+   *        Title of the page being sent.
+   */
+  sendURIToClientForDisplay: function sendURIToClientForDisplay(uri, clientId, title) {
+    this._log.info("Sending URI to client: " + uri + " -> " +
+                   clientId + " (" + title + ")");
+    this.sendCommand("displayURI", [uri, this.localID, title], clientId);
+
+    this._tracker.score += SCORE_INCREMENT_XLARGE;
+  },
+
+  /**
+   * Handle a bunch of received 'displayURI' commands.
+   *
+   * 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:
+   *
+   *   uri       URI (string) that is requested for display.
+   *   clientId  ID of client that sent the command.
+   *   title     Title of page that loaded URI (likely) corresponds to.
+   *
+   * The 'data' parameter to the callback will not be defined.
+   *
+   * @param uris
+   *        An array containing URI objects to display
+   * @param uris[].uri
+   *        String URI that was received
+   * @param uris[].clientId
+   *        ID of client that sent URI
+   * @param uris[].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);
+  },
+
+  _removeRemoteClient(id) {
+    delete this._store._remoteClients[id];
+    this._tracker.removeChangedID(id);
+  },
+};
+
+function ClientStore(name, engine) {
+  Store.call(this, name, engine);
+}
+ClientStore.prototype = {
+  __proto__: Store.prototype,
+
+  _remoteClients: {},
+
+  create(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
+      this.engine.localCommands = record.commands;
+    } 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.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;
+      record.application = this.engine.brandName   // "Nightly"
+
+      // We can't compute these yet.
+      // record.device = "";            // Bug 1100723
+      // 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;
+  },
+
+  itemExists(id) {
+    return id in this.getAllIDs();
+  },
+
+  getAllIDs: function getAllIDs() {
+    let ids = {};
+    ids[this.engine.localID] = true;
+    for (let id in this._remoteClients)
+      ids[id] = true;
+    return ids;
+  },
+
+  wipe: function wipe() {
+    this._remoteClients = {};
+  },
+};
+
+function ClientsTracker(name, engine) {
+  Tracker.call(this, name, engine);
+  Svc.Obs.add("weave:engine:start-tracking", this);
+  Svc.Obs.add("weave:engine:stop-tracking", this);
+}
+ClientsTracker.prototype = {
+  __proto__: Tracker.prototype,
+
+  _enabled: false,
+
+  observe: function observe(subject, topic, data) {
+    switch (topic) {
+      case "weave:engine:start-tracking":
+        if (!this._enabled) {
+          Svc.Prefs.observe("client.name", this);
+          this._enabled = true;
+        }
+        break;
+      case "weave:engine:stop-tracking":
+        if (this._enabled) {
+          Svc.Prefs.ignore("client.name", this);
+          this._enabled = false;
+        }
+        break;
+      case "nsPref:changed":
+        this._log.debug("client.name preference changed");
+        this.addChangedID(Svc.Prefs.get("client.GUID"));
+        this.score += SCORE_INCREMENT_XLARGE;
+        break;
+    }
+  }
+};
diff --git a/services/sync/modules/engines/extension-storage.js b/services/sync/modules/engines/extension-storage.js
new file mode 100644
index 000000000..f8f15b128
--- /dev/null
+++ b/services/sync/modules/engines/extension-storage.js
@@ -0,0 +1,277 @@
+/* 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 = ['ExtensionStorageEngine', 'EncryptionRemoteTransformer',
+                         'KeyRingEncryptionRemoteTransformer'];
+
+const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
+
+Cu.import("resource://services-crypto/utils.js");
+Cu.import("resource://services-sync/constants.js");
+Cu.import("resource://services-sync/engines.js");
+Cu.import("resource://services-sync/keys.js");
+Cu.import("resource://services-sync/util.js");
+Cu.import("resource://services-common/async.js");
+XPCOMUtils.defineLazyModuleGetter(this, "ExtensionStorageSync",
+                                  "resource://gre/modules/ExtensionStorageSync.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "fxAccounts",
+                                  "resource://gre/modules/FxAccounts.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+                                  "resource://gre/modules/Task.jsm");
+
+/**
+ * The Engine that manages syncing for the web extension "storage"
+ * API, and in particular ext.storage.sync.
+ *
+ * ext.storage.sync is implemented using Kinto, so it has mechanisms
+ * for syncing that we do not need to integrate in the Firefox Sync
+ * framework, so this is something of a stub.
+ */
+this.ExtensionStorageEngine = function ExtensionStorageEngine(service) {
+  SyncEngine.call(this, "Extension-Storage", service);
+};
+ExtensionStorageEngine.prototype = {
+  __proto__: SyncEngine.prototype,
+  _trackerObj: ExtensionStorageTracker,
+  // we don't need these since we implement our own sync logic
+  _storeObj: undefined,
+  _recordObj: undefined,
+
+  syncPriority: 10,
+  allowSkippedRecord: false,
+
+  _sync: function () {
+    return Async.promiseSpinningly(ExtensionStorageSync.syncAll());
+  },
+
+  get enabled() {
+    // By default, we sync extension storage if we sync addons. This
+    // lets us simplify the UX since users probably don't consider
+    // "extension preferences" a separate category of syncing.
+    // However, we also respect engine.extension-storage.force, which
+    // can be set to true or false, if a power user wants to customize
+    // the behavior despite the lack of UI.
+    const forced = Svc.Prefs.get("engine." + this.prefName + ".force", undefined);
+    if (forced !== undefined) {
+      return forced;
+    }
+    return Svc.Prefs.get("engine.addons", false);
+  },
+};
+
+function ExtensionStorageTracker(name, engine) {
+  Tracker.call(this, name, engine);
+}
+ExtensionStorageTracker.prototype = {
+  __proto__: Tracker.prototype,
+
+  startTracking: function () {
+    Svc.Obs.add("ext.storage.sync-changed", this);
+  },
+
+  stopTracking: function () {
+    Svc.Obs.remove("ext.storage.sync-changed", this);
+  },
+
+  observe: function (subject, topic, data) {
+    Tracker.prototype.observe.call(this, subject, topic, data);
+
+    if (this.ignoreAll) {
+      return;
+    }
+
+    if (topic !== "ext.storage.sync-changed") {
+      return;
+    }
+
+    // Single adds, removes and changes are not so important on their
+    // own, so let's just increment score a bit.
+    this.score += SCORE_INCREMENT_MEDIUM;
+  },
+
+  // Override a bunch of methods which don't do anything for us.
+  // This is a performance hack.
+  saveChangedIDs: function() {
+  },
+  loadChangedIDs: function() {
+  },
+  ignoreID: function() {
+  },
+  unignoreID: function() {
+  },
+  addChangedID: function() {
+  },
+  removeChangedID: function() {
+  },
+  clearChangedIDs: function() {
+  },
+};
+
+/**
+ * Utility function to enforce an order of fields when computing an HMAC.
+ */
+function ciphertextHMAC(keyBundle, id, IV, ciphertext) {
+  const hasher = keyBundle.sha256HMACHasher;
+  return Utils.bytesAsHex(Utils.digestUTF8(id + IV + ciphertext, hasher));
+}
+
+/**
+ * A "remote transformer" that the Kinto library will use to
+ * encrypt/decrypt records when syncing.
+ *
+ * This is an "abstract base class". Subclass this and override
+ * getKeys() to use it.
+ */
+class EncryptionRemoteTransformer {
+  encode(record) {
+    const self = this;
+    return Task.spawn(function* () {
+      const keyBundle = yield self.getKeys();
+      if (record.ciphertext) {
+        throw new Error("Attempt to reencrypt??");
+      }
+      let id = record.id;
+      if (!record.id) {
+        throw new Error("Record ID is missing or invalid");
+      }
+
+      let IV = Svc.Crypto.generateRandomIV();
+      let ciphertext = Svc.Crypto.encrypt(JSON.stringify(record),
+                                          keyBundle.encryptionKeyB64, IV);
+      let hmac = ciphertextHMAC(keyBundle, id, IV, ciphertext);
+      const encryptedResult = {ciphertext, IV, hmac, id};
+      if (record.hasOwnProperty("last_modified")) {
+        encryptedResult.last_modified = record.last_modified;
+      }
+      return encryptedResult;
+    });
+  }
+
+  decode(record) {
+    const self = this;
+    return Task.spawn(function* () {
+      if (!record.ciphertext) {
+        // This can happen for tombstones if a record is deleted.
+        if (record.deleted) {
+          return record;
+        }
+        throw new Error("No ciphertext: nothing to decrypt?");
+      }
+      const keyBundle = yield self.getKeys();
+      // Authenticate the encrypted blob with the expected HMAC
+      let computedHMAC = ciphertextHMAC(keyBundle, record.id, record.IV, record.ciphertext);
+
+      if (computedHMAC != record.hmac) {
+        Utils.throwHMACMismatch(record.hmac, computedHMAC);
+      }
+
+      // Handle invalid data here. Elsewhere we assume that cleartext is an object.
+      let cleartext = Svc.Crypto.decrypt(record.ciphertext,
+                                         keyBundle.encryptionKeyB64, record.IV);
+      let jsonResult = JSON.parse(cleartext);
+      if (!jsonResult || typeof jsonResult !== "object") {
+        throw new Error("Decryption failed: result is <" + jsonResult + ">, not an object.");
+      }
+
+      // Verify that the encrypted id matches the requested record's id.
+      // This should always be true, because we compute the HMAC over
+      // the original record's ID, and that was verified already (above).
+      if (jsonResult.id != record.id) {
+        throw new Error("Record id mismatch: " + jsonResult.id + " != " + record.id);
+      }
+
+      if (record.hasOwnProperty("last_modified")) {
+        jsonResult.last_modified = record.last_modified;
+      }
+
+      return jsonResult;
+    });
+  }
+
+  /**
+   * Retrieve keys to use during encryption.
+   *
+   * Returns a Promise<KeyBundle>.
+   */
+  getKeys() {
+    throw new Error("override getKeys in a subclass");
+  }
+}
+// You can inject this
+EncryptionRemoteTransformer.prototype._fxaService = fxAccounts;
+
+/**
+ * An EncryptionRemoteTransformer that provides a keybundle derived
+ * from the user's kB, suitable for encrypting a keyring.
+ */
+class KeyRingEncryptionRemoteTransformer extends EncryptionRemoteTransformer {
+  getKeys() {
+    const self = this;
+    return Task.spawn(function* () {
+      const user = yield self._fxaService.getSignedInUser();
+      // FIXME: we should permit this if the user is self-hosting
+      // their storage
+      if (!user) {
+        throw new Error("user isn't signed in to FxA; can't sync");
+      }
+
+      if (!user.kB) {
+        throw new Error("user doesn't have kB");
+      }
+
+      let kB = Utils.hexToBytes(user.kB);
+
+      let keyMaterial = CryptoUtils.hkdf(kB, undefined,
+                                       "identity.mozilla.com/picl/v1/chrome.storage.sync", 2*32);
+      let bundle = new BulkKeyBundle();
+      // [encryptionKey, hmacKey]
+      bundle.keyPair = [keyMaterial.slice(0, 32), keyMaterial.slice(32, 64)];
+      return bundle;
+    });
+  }
+  // Pass through the kbHash field from the unencrypted record. If
+  // encryption fails, we can use this to try to detect whether we are
+  // being compromised or if the record here was encoded with a
+  // different kB.
+  encode(record) {
+    const encodePromise = super.encode(record);
+    return Task.spawn(function* () {
+      const encoded = yield encodePromise;
+      encoded.kbHash = record.kbHash;
+      return encoded;
+    });
+  }
+
+  decode(record) {
+    const decodePromise = super.decode(record);
+    return Task.spawn(function* () {
+      try {
+        return yield decodePromise;
+      } catch (e) {
+        if (Utils.isHMACMismatch(e)) {
+          const currentKBHash = yield ExtensionStorageSync.getKBHash();
+          if (record.kbHash != currentKBHash) {
+            // Some other client encoded this with a kB that we don't
+            // have access to.
+            KeyRingEncryptionRemoteTransformer.throwOutdatedKB(currentKBHash, record.kbHash);
+          }
+        }
+        throw e;
+      }
+    });
+  }
+
+  // Generator and discriminator for KB-is-outdated exceptions.
+  static throwOutdatedKB(shouldBe, is) {
+    throw new Error(`kB hash on record is outdated: should be ${shouldBe}, is ${is}`);
+  }
+
+  static isOutdatedKB(exc) {
+    const kbMessage = "kB hash on record is outdated: ";
+    return exc && exc.message && exc.message.indexOf &&
+      (exc.message.indexOf(kbMessage) == 0);
+  }
+}
diff --git a/services/sync/modules/engines/forms.js b/services/sync/modules/engines/forms.js
new file mode 100644
index 000000000..43f79d4f7
--- /dev/null
+++ b/services/sync/modules/engines/forms.js
@@ -0,0 +1,305 @@
+/* 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/. */
+
+this.EXPORTED_SYMBOLS = ['FormEngine', 'FormRec', 'FormValidator'];
+
+var Cc = Components.classes;
+var Ci = Components.interfaces;
+var Cu = Components.utils;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://services-sync/engines.js");
+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.
+
+this.FormRec = function FormRec(collection, id) {
+  CryptoWrapper.call(this, collection, id);
+}
+FormRec.prototype = {
+  __proto__: CryptoWrapper.prototype,
+  _logName: "Sync.Record.Form",
+  ttl: FORMS_TTL
+};
+
+Utils.deferGetSet(FormRec, "cleartext", ["name", "value"]);
+
+
+var 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));
+  },
+
+  _updateSpinningly: function(changes) {
+    if (!Svc.FormHistory.enabled) {
+      return; // update isn't going to do anything.
+    }
+    let cb = Async.makeSpinningCallback();
+    let callbacks = {
+      handleCompletion: function(reason) {
+        cb();
+      }
+    };
+    Svc.FormHistory.update(changes, callbacks);
+    return cb.wait();
+  },
+
+  getEntry: function (guid) {
+    let results = this._searchSpinningly(this._getEntryCols, {guid: guid});
+    if (!results.length) {
+      return null;
+    }
+    return {name: results[0].fieldname, value: results[0].value};
+  },
+
+  getGUID: function (name, value) {
+    // Query for the provided entry.
+    let query = { fieldname: name, value: value };
+    let results = this._searchSpinningly(this._guidCols, query);
+    return results.length ? results[0].guid : null;
+  },
+
+  hasGUID: function (guid) {
+    // We could probably use a count function here, but searchSpinningly exists...
+    return this._searchSpinningly(this._guidCols, {guid: guid}).length != 0;
+  },
+
+  replaceGUID: function (oldGUID, newGUID) {
+    let changes = {
+      op: "update",
+      guid: oldGUID,
+      newGuid: newGUID,
+    }
+    this._updateSpinningly(changes);
+  }
+
+};
+
+this.FormEngine = function FormEngine(service) {
+  SyncEngine.call(this, "Forms", service);
+}
+FormEngine.prototype = {
+  __proto__: SyncEngine.prototype,
+  _storeObj: FormStore,
+  _trackerObj: FormTracker,
+  _recordObj: FormRec,
+  applyIncomingBatchSize: FORMS_STORE_BATCH_SIZE,
+
+  syncPriority: 6,
+
+  get prefName() {
+    return "history";
+  },
+
+  _findDupe: function _findDupe(item) {
+    return FormWrapper.getGUID(item.name, item.value);
+  }
+};
+
+function FormStore(name, engine) {
+  Store.call(this, name, engine);
+}
+FormStore.prototype = {
+  __proto__: Store.prototype,
+
+  _processChange: function (change) {
+    // If this._changes is defined, then we are applying a batch, so we
+    // can defer it.
+    if (this._changes) {
+      this._changes.push(change);
+      return;
+    }
+
+    // Otherwise we must handle the change synchronously, right now.
+    FormWrapper._updateSpinningly(change);
+  },
+
+  applyIncomingBatch: function (records) {
+    // We collect all the changes to be made then apply them all at once.
+    this._changes = [];
+    let failures = Store.prototype.applyIncomingBatch.call(this, records);
+    if (this._changes.length) {
+      FormWrapper._updateSpinningly(this._changes);
+    }
+    delete this._changes;
+    return failures;
+  },
+
+  getAllIDs: function () {
+    let results = FormWrapper._searchSpinningly(["guid"], [])
+    let guids = {};
+    for (let result of results) {
+      guids[result.guid] = true;
+    }
+    return guids;
+  },
+
+  changeItemID: function (oldID, newID) {
+    FormWrapper.replaceGUID(oldID, newID);
+  },
+
+  itemExists: function (id) {
+    return FormWrapper.hasGUID(id);
+  },
+
+  createRecord: function (id, collection) {
+    let record = new FormRec(collection, id);
+    let entry = FormWrapper.getEntry(id);
+    if (entry != null) {
+      record.name = entry.name;
+      record.value = entry.value;
+    } else {
+      record.deleted = true;
+    }
+    return record;
+  },
+
+  create: function (record) {
+    this._log.trace("Adding form record for " + record.name);
+    let change = {
+      op: "add",
+      fieldname: record.name,
+      value: record.value
+    };
+    this._processChange(change);
+  },
+
+  remove: function (record) {
+    this._log.trace("Removing form record: " + record.id);
+    let change = {
+      op: "remove",
+      guid: record.id
+    };
+    this._processChange(change);
+  },
+
+  update: function (record) {
+    this._log.trace("Ignoring form record update request!");
+  },
+
+  wipe: function () {
+    let change = {
+      op: "remove"
+    };
+    FormWrapper._updateSpinningly(change);
+  }
+};
+
+function FormTracker(name, engine) {
+  Tracker.call(this, name, engine);
+}
+FormTracker.prototype = {
+  __proto__: Tracker.prototype,
+
+  QueryInterface: XPCOMUtils.generateQI([
+    Ci.nsIObserver,
+    Ci.nsISupportsWeakReference]),
+
+  startTracking: function() {
+    Svc.Obs.add("satchel-storage-changed", this);
+  },
+
+  stopTracking: function() {
+    Svc.Obs.remove("satchel-storage-changed", this);
+  },
+
+  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") {
+          let guid = subject.QueryInterface(Ci.nsISupportsString).toString();
+          this.trackEntry(guid);
+        }
+        break;
+    }
+  },
+
+  trackEntry: function (guid) {
+    this.addChangedID(guid);
+    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
new file mode 100644
index 000000000..307d484c1
--- /dev/null
+++ b/services/sync/modules/engines/history.js
@@ -0,0 +1,442 @@
+/* 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/. */
+
+this.EXPORTED_SYMBOLS = ['HistoryEngine', 'HistoryRec'];
+
+var Cc = Components.classes;
+var Ci = Components.interfaces;
+var Cu = Components.utils;
+var Cr = Components.results;
+
+const HISTORY_TTL = 5184000; // 60 days
+
+Cu.import("resource://gre/modules/PlacesUtils.jsm", this);
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://services-common/async.js");
+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/record.js");
+Cu.import("resource://services-sync/util.js");
+
+this.HistoryRec = function HistoryRec(collection, id) {
+  CryptoWrapper.call(this, collection, id);
+}
+HistoryRec.prototype = {
+  __proto__: CryptoWrapper.prototype,
+  _logName: "Sync.Record.History",
+  ttl: HISTORY_TTL
+};
+
+Utils.deferGetSet(HistoryRec, "cleartext", ["histUri", "title", "visits"]);
+
+
+this.HistoryEngine = function HistoryEngine(service) {
+  SyncEngine.call(this, "History", service);
+}
+HistoryEngine.prototype = {
+  __proto__: SyncEngine.prototype,
+  _recordObj: HistoryRec,
+  _storeObj: HistoryStore,
+  _trackerObj: HistoryTracker,
+  downloadLimit: MAX_HISTORY_DOWNLOAD,
+  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) {
+  Store.call(this, 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;
+      stmt.finalize();
+    }
+    this._stmts = {};
+  }, this);
+}
+HistoryStore.prototype = {
+  __proto__: Store.prototype,
+
+  __asyncHistory: null,
+  get _asyncHistory() {
+    if (!this.__asyncHistory) {
+      this.__asyncHistory = Cc["@mozilla.org/browser/history;1"]
+                              .getService(Ci.mozIAsyncHistory);
+    }
+    return this.__asyncHistory;
+  },
+
+  _stmts: {},
+  _getStmt: function(query) {
+    if (query in this._stmts) {
+      return this._stmts[query];
+    }
+
+    this._log.trace("Creating SQL statement: " + query);
+    let db = PlacesUtils.history.QueryInterface(Ci.nsPIPlacesDatabase)
+                        .DBConnection;
+    return this._stmts[query] = db.createAsyncStatement(query);
+  },
+
+  get _setGUIDStm() {
+    return this._getStmt(
+      "UPDATE moz_places " +
+      "SET guid = :guid " +
+      "WHERE url_hash = hash(:page_url) AND url = :page_url");
+  },
+
+  // Some helper functions to handle GUIDs
+  setGUID: function setGUID(uri, guid) {
+    uri = uri.spec ? uri.spec : uri;
+
+    if (!guid) {
+      guid = Utils.makeGUID();
+    }
+
+    let stmt = this._setGUIDStm;
+    stmt.params.guid = guid;
+    stmt.params.page_url = uri;
+    Async.querySpinningly(stmt);
+    return guid;
+  },
+
+  get _guidStm() {
+    return this._getStmt(
+      "SELECT guid " +
+      "FROM moz_places " +
+      "WHERE url_hash = hash(:page_url) AND url = :page_url");
+  },
+  _guidCols: ["guid"],
+
+  GUIDForUri: function GUIDForUri(uri, create) {
+    let stm = this._guidStm;
+    stm.params.page_url = uri.spec ? uri.spec : uri;
+
+    // Use the existing GUID if it exists
+    let result = Async.querySpinningly(stm, this._guidCols)[0];
+    if (result && result.guid)
+      return result.guid;
+
+    // Give the uri a GUID if it doesn't have one
+    if (create)
+      return this.setGUID(uri);
+  },
+
+  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`);
+  },
+  _visitCols: ["date", "type"],
+
+  get _urlStm() {
+    return this._getStmt(
+      "SELECT url, title, frecency " +
+      "FROM moz_places " +
+      "WHERE guid = :guid");
+  },
+  _urlCols: ["url", "title", "frecency"],
+
+  get _allUrlStm() {
+    return this._getStmt(
+      "SELECT url " +
+      "FROM moz_places " +
+      "WHERE last_visit_date > :cutoff_date " +
+      "ORDER BY frecency DESC " +
+      "LIMIT :max_results");
+  },
+  _allUrlCols: ["url"],
+
+  // See bug 320831 for why we use SQL here
+  _getVisits: function HistStore__getVisits(uri) {
+    this._visitStm.params.url = uri;
+    return Async.querySpinningly(this._visitStm, this._visitCols);
+  },
+
+  // See bug 468732 for why we use SQL here
+  _findURLByGUID: function HistStore__findURLByGUID(guid) {
+    this._urlStm.params.guid = guid;
+    return Async.querySpinningly(this._urlStm, this._urlCols)[0];
+  },
+
+  changeItemID: function HStore_changeItemID(oldID, newID) {
+    this.setGUID(this._findURLByGUID(oldID).url, newID);
+  },
+
+
+  getAllIDs: function HistStore_getAllIDs() {
+    // Only get places visited within the last 30 days (30*24*60*60*1000ms)
+    this._allUrlStm.params.cutoff_date = (Date.now() - 2592000000) * 1000;
+    this._allUrlStm.params.max_results = MAX_HISTORY_UPLOAD;
+
+    let urls = Async.querySpinningly(this._allUrlStm, this._allUrlCols);
+    let self = this;
+    return urls.reduce(function(ids, item) {
+      ids[self.GUIDForUri(item.url, true)] = item.url;
+      return ids;
+    }, {});
+  },
+
+  applyIncomingBatch: function applyIncomingBatch(records) {
+    let failed = [];
+
+    // Convert incoming records to mozIPlaceInfo objects. Some records can be
+    // ignored or handled directly, so we're rewriting the array in-place.
+    let i, k;
+    for (i = 0, k = 0; i < records.length; i++) {
+      let record = records[k] = records[i];
+      let shouldApply;
+
+      // This is still synchronous I/O for now.
+      try {
+        if (record.deleted) {
+          // Consider using nsIBrowserHistory::removePages() here.
+          this.remove(record);
+          // No further processing needed. Remove it from the list.
+          shouldApply = false;
+        } else {
+          shouldApply = this._recordToPlaceInfo(record);
+        }
+      } catch (ex) {
+        if (Async.isShutdownException(ex)) {
+          throw ex;
+        }
+        failed.push(record.id);
+        shouldApply = false;
+      }
+
+      if (shouldApply) {
+        k += 1;
+      }
+    }
+    records.length = k; // truncate array
+
+    // Nothing to do.
+    if (!records.length) {
+      return failed;
+    }
+
+    let updatePlacesCallback = { 
+      handleResult: function handleResult() {},
+      handleError: function handleError(resultCode, placeInfo) {
+        failed.push(placeInfo.guid);
+      },
+      handleCompletion: Async.makeSyncCallback()
+    };
+    this._asyncHistory.updatePlaces(records, updatePlacesCallback);
+    Async.waitForSyncCallback(updatePlacesCallback.handleCompletion);
+    return failed;
+  },
+
+  /**
+   * Converts a Sync history record to a mozIPlaceInfo.
+   * 
+   * Throws if an invalid record is encountered (invalid URI, etc.),
+   * returns true if the record is to be applied, false otherwise
+   * (no visits to add, etc.),
+   */
+  _recordToPlaceInfo: function _recordToPlaceInfo(record) {
+    // Sort out invalid URIs and ones Places just simply doesn't want.
+    record.uri = Utils.makeURI(record.histUri);
+    if (!record.uri) {
+      this._log.warn("Attempted to process invalid URI, skipping.");
+      throw "Invalid URI in record";
+    }
+
+    if (!Utils.checkGUID(record.id)) {
+      this._log.warn("Encountered record with invalid GUID: " + record.id);
+      return false;
+    }
+    record.guid = record.id;
+
+    if (!PlacesUtils.history.canAddURI(record.uri)) {
+      this._log.trace("Ignoring record " + record.id + " with URI "
+                      + record.uri.spec + ": can't add this URI.");
+      return false;
+    }
+
+    // We dupe visits by date and type. So an incoming visit that has
+    // the same timestamp and type as a local one won't get applied.
+    // To avoid creating new objects, we rewrite the query result so we
+    // can simply check for containment below.
+    let curVisits = this._getVisits(record.histUri);
+    let i, k;
+    for (i = 0; i < curVisits.length; i++) {
+      curVisits[i] = curVisits[i].date + "," + curVisits[i].type;
+    }
+
+    // Walk through the visits, make sure we have sound data, and eliminate
+    // dupes. The latter is done by rewriting the array in-place.
+    for (i = 0, k = 0; i < record.visits.length; i++) {
+      let visit = record.visits[k] = record.visits[i];
+
+      if (!visit.date || typeof visit.date != "number") {
+        this._log.warn("Encountered record with invalid visit date: "
+                       + visit.date);
+        continue;
+      }
+
+      if (!visit.type ||
+          !Object.values(PlacesUtils.history.TRANSITIONS).includes(visit.type)) {
+        this._log.warn("Encountered record with invalid visit type: " +
+                       visit.type + "; ignoring.");
+        continue;
+      }
+
+      // Dates need to be integers.
+      visit.date = Math.round(visit.date);
+
+      if (curVisits.indexOf(visit.date + "," + visit.type) != -1) {
+        // Visit is a dupe, don't increment 'k' so the element will be
+        // overwritten.
+        continue;
+      }
+
+      visit.visitDate = visit.date;
+      visit.transitionType = visit.type;
+      k += 1;
+    }
+    record.visits.length = k; // truncate array
+
+    // No update if there aren't any visits to apply.
+    // mozIAsyncHistory::updatePlaces() wants at least one visit.
+    // In any case, the only thing we could change would be the title
+    // and that shouldn't change without a visit.
+    if (!record.visits.length) {
+      this._log.trace("Ignoring record " + record.id + " with URI "
+                      + record.uri.spec + ": no visits to add.");
+      return false;
+    }
+
+    return true;
+  },
+
+  remove: function HistStore_remove(record) {
+    let page = this._findURLByGUID(record.id);
+    if (page == null) {
+      this._log.debug("Page already removed: " + record.id);
+      return;
+    }
+
+    let uri = Utils.makeURI(page.url);
+    PlacesUtils.history.removePage(uri);
+    this._log.trace("Removed page: " + [record.id, page.url, page.title]);
+  },
+
+  itemExists: function HistStore_itemExists(id) {
+    return !!this._findURLByGUID(id);
+  },
+
+  createRecord: function createRecord(id, collection) {
+    let foo = this._findURLByGUID(id);
+    let record = new HistoryRec(collection, id);
+    if (foo) {
+      record.histUri = foo.url;
+      record.title = foo.title;
+      record.sortindex = foo.frecency;
+      record.visits = this._getVisits(record.histUri);
+    } else {
+      record.deleted = true;
+    }
+
+    return record;
+  },
+
+  wipe: function HistStore_wipe() {
+    let cb = Async.makeSyncCallback();
+    PlacesUtils.history.clear().then(result => {cb(null, result)}, err => {cb(err)});
+    return Async.waitForSyncCallback(cb);
+  }
+};
+
+function HistoryTracker(name, engine) {
+  Tracker.call(this, name, engine);
+}
+HistoryTracker.prototype = {
+  __proto__: Tracker.prototype,
+
+  startTracking: function() {
+    this._log.info("Adding Places observer.");
+    PlacesUtils.history.addObserver(this, true);
+  },
+
+  stopTracking: function() {
+    this._log.info("Removing Places observer.");
+    PlacesUtils.history.removeObserver(this);
+  },
+
+  QueryInterface: XPCOMUtils.generateQI([
+    Ci.nsINavHistoryObserver,
+    Ci.nsISupportsWeakReference
+  ]),
+
+  onDeleteAffectsGUID: function (uri, guid, reason, source, increment) {
+    if (this.ignoreAll || reason == Ci.nsINavHistoryObserver.REASON_EXPIRED) {
+      return;
+    }
+    this._log.trace(source + ": " + uri.spec + ", reason " + reason);
+    if (this.addChangedID(guid)) {
+      this.score += increment;
+    }
+  },
+
+  onDeleteVisits: function (uri, visitTime, guid, reason) {
+    this.onDeleteAffectsGUID(uri, guid, reason, "onDeleteVisits", SCORE_INCREMENT_SMALL);
+  },
+
+  onDeleteURI: function (uri, guid, reason) {
+    this.onDeleteAffectsGUID(uri, guid, reason, "onDeleteURI", SCORE_INCREMENT_XLARGE);
+  },
+
+  onVisit: function (uri, vid, time, session, referrer, trans, guid) {
+    if (this.ignoreAll) {
+      this._log.trace("ignoreAll: ignoring visit for " + guid);
+      return;
+    }
+
+    this._log.trace("onVisit: " + uri.spec);
+    if (this.addChangedID(guid)) {
+      this.score += SCORE_INCREMENT_SMALL;
+    }
+  },
+
+  onClearHistory: function () {
+    this._log.trace("onClearHistory");
+    // Note that we're going to trigger a sync, but none of the cleared
+    // pages are tracked, so the deletions will not be propagated.
+    // See Bug 578694.
+    this.score += SCORE_INCREMENT_XLARGE;
+  },
+
+  onBeginUpdateBatch: function () {},
+  onEndUpdateBatch: function () {},
+  onPageChanged: function () {},
+  onTitleChanged: function () {},
+  onBeforeDeleteURI: function () {},
+};
diff --git a/services/sync/modules/engines/passwords.js b/services/sync/modules/engines/passwords.js
new file mode 100644
index 000000000..51db49a0a
--- /dev/null
+++ b/services/sync/modules/engines/passwords.js
@@ -0,0 +1,371 @@
+/* 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/. */
+
+this.EXPORTED_SYMBOLS = ['PasswordEngine', 'LoginRec', 'PasswordValidator'];
+
+var {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);
+}
+LoginRec.prototype = {
+  __proto__: CryptoWrapper.prototype,
+  _logName: "Sync.Record.Login",
+};
+
+Utils.deferGetSet(LoginRec, "cleartext", [
+    "hostname", "formSubmitURL",
+    "httpRealm", "username", "password", "usernameField", "passwordField",
+    "timeCreated", "timePasswordChanged",
+    ]);
+
+
+this.PasswordEngine = function PasswordEngine(service) {
+  SyncEngine.call(this, "Passwords", service);
+}
+PasswordEngine.prototype = {
+  __proto__: SyncEngine.prototype,
+  _storeObj: PasswordStore,
+  _trackerObj: PasswordTracker,
+  _recordObj: LoginRec,
+
+  applyIncomingBatchSize: PASSWORDS_STORE_BATCH_SIZE,
+
+  syncPriority: 2,
+
+  _syncFinish: function () {
+    SyncEngine.prototype._syncFinish.call(this);
+
+    // Delete the Weave credentials from the server once.
+    if (!Svc.Prefs.get("deletePwdFxA", false)) {
+      try {
+        let ids = [];
+        for (let host of Utils.getSyncCredentialsHosts()) {
+          for (let info of Services.logins.findLogins({}, host, "", "")) {
+            ids.push(info.QueryInterface(Components.interfaces.nsILoginMetaInfo).guid);
+          }
+        }
+        if (ids.length) {
+          let coll = new Collection(this.engineURL, null, this.service);
+          coll.ids = ids;
+          let ret = coll.delete();
+          this._log.debug("Delete result: " + ret);
+          if (!ret.success && ret.status != 400) {
+            // A non-400 failure means try again next time.
+            return;
+          }
+        } else {
+          this._log.debug("Didn't find any passwords to delete");
+        }
+        // If there were no ids to delete, or we succeeded, or got a 400,
+        // record success.
+        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);
+      }
+    }
+  },
+
+  _findDupe: function (item) {
+    let login = this._store._nsLoginInfoFromRecord(item);
+    if (!login) {
+      return;
+    }
+
+    let logins = Services.logins.findLogins({}, login.hostname, login.formSubmitURL, login.httpRealm);
+
+    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) {
+      if (login.matches(local, true) && local instanceof Ci.nsILoginMetaInfo) {
+        return local.guid;
+      }
+    }
+  },
+};
+
+function PasswordStore(name, engine) {
+  Store.call(this, name, engine);
+  this._nsLoginInfo = new Components.Constructor("@mozilla.org/login-manager/loginInfo;1", Ci.nsILoginInfo, "init");
+}
+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;
+    }
+
+    if (record.formSubmitURL && record.httpRealm) {
+      this._log.warn("Record " + record.id + " has both formSubmitURL and httpRealm. Skipping.");
+      return null;
+    }
+
+    // Passing in "undefined" results in an empty string, which later
+    // counts as a value. Explicitly `|| null` these fields according to JS
+    // truthiness. Records with empty strings or null will be unmolested.
+    let info = new this._nsLoginInfo(record.hostname,
+                                     nullUndefined(record.formSubmitURL),
+                                     nullUndefined(record.httpRealm),
+                                     record.username,
+                                     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();
+    prop.setPropertyAsAUTF8String("guid", id);
+
+    let logins = Services.logins.searchLogins({}, prop);
+    this._sleep(0); // Yield back to main thread after synchronous operation.
+
+    if (logins.length > 0) {
+      this._log.trace(logins.length + " items matching " + id + " found.");
+      return logins[0];
+    }
+
+    this._log.trace("No items matching " + id + " found. Ignoring");
+    return null;
+  },
+
+  getAllIDs: function () {
+    let items = {};
+    let logins = Services.logins.getAllLogins({});
+
+    for (let i = 0; i < logins.length; i++) {
+      // Skip over Weave password/passphrase entries.
+      let metaInfo = logins[i].QueryInterface(Ci.nsILoginMetaInfo);
+      if (Utils.getSyncCredentialsHosts().has(metaInfo.hostname)) {
+        continue;
+      }
+
+      items[metaInfo.guid] = metaInfo;
+    }
+
+    return items;
+  },
+
+  changeItemID: function (oldID, newID) {
+    this._log.trace("Changing item ID: " + oldID + " to " + newID);
+
+    let oldLogin = this._getLoginFromGUID(oldID);
+    if (!oldLogin) {
+      this._log.trace("Can't change item ID: item doesn't exist");
+      return;
+    }
+    if (this._getLoginFromGUID(newID)) {
+      this._log.trace("Can't change item ID: new ID already in use");
+      return;
+    }
+
+    let prop = this._newPropertyBag();
+    prop.setPropertyAsAUTF8String("guid", newID);
+
+    Services.logins.modifyLogin(oldLogin, prop);
+  },
+
+  itemExists: function (id) {
+    return !!this._getLoginFromGUID(id);
+  },
+
+  createRecord: function (id, collection) {
+    let record = new LoginRec(collection, id);
+    let login = this._getLoginFromGUID(id);
+
+    if (!login) {
+      record.deleted = true;
+      return record;
+    }
+
+    record.hostname = login.hostname;
+    record.formSubmitURL = login.formSubmitURL;
+    record.httpRealm = login.httpRealm;
+    record.username = login.username;
+    record.password = login.password;
+    record.usernameField = login.usernameField;
+    record.passwordField = login.passwordField;
+
+    // Optional fields.
+    login.QueryInterface(Ci.nsILoginMetaInfo);
+    record.timeCreated = login.timeCreated;
+    record.timePasswordChanged = login.timePasswordChanged;
+
+    return record;
+  },
+
+  create: function (record) {
+    let login = this._nsLoginInfoFromRecord(record);
+    if (!login) {
+      return;
+    }
+
+    this._log.debug("Adding login for " + record.hostname);
+    this._log.trace("httpRealm: " + JSON.stringify(login.httpRealm) + "; " +
+                    "formSubmitURL: " + JSON.stringify(login.formSubmitURL));
+    try {
+      Services.logins.addLogin(login);
+    } catch(ex) {
+      this._log.debug(`Adding record ${record.id} resulted in exception`, ex);
+    }
+  },
+
+  remove: function (record) {
+    this._log.trace("Removing login " + record.id);
+
+    let loginItem = this._getLoginFromGUID(record.id);
+    if (!loginItem) {
+      this._log.trace("Asked to remove record that doesn't exist, ignoring");
+      return;
+    }
+
+    Services.logins.removeLogin(loginItem);
+  },
+
+  update: function (record) {
+    let loginItem = this._getLoginFromGUID(record.id);
+    if (!loginItem) {
+      this._log.debug("Skipping update for unknown item: " + record.hostname);
+      return;
+    }
+
+    this._log.debug("Updating " + record.hostname);
+    let newinfo = this._nsLoginInfoFromRecord(record);
+    if (!newinfo) {
+      return;
+    }
+
+    try {
+      Services.logins.modifyLogin(loginItem, newinfo);
+    } catch(ex) {
+      this._log.debug(`Modifying record ${record.id} resulted in exception; not modifying`, ex);
+    }
+  },
+
+  wipe: function () {
+    Services.logins.removeAllLogins();
+  },
+};
+
+function PasswordTracker(name, engine) {
+  Tracker.call(this, name, engine);
+  Svc.Obs.add("weave:engine:start-tracking", this);
+  Svc.Obs.add("weave:engine:stop-tracking", this);
+}
+PasswordTracker.prototype = {
+  __proto__: Tracker.prototype,
+
+  startTracking: function () {
+    Svc.Obs.add("passwordmgr-storage-changed", this);
+  },
+
+  stopTracking: function () {
+    Svc.Obs.remove("passwordmgr-storage-changed", this);
+  },
+
+  observe: function (subject, topic, data) {
+    Tracker.prototype.observe.call(this, subject, topic, data);
+
+    if (this.ignoreAll) {
+      return;
+    }
+
+    // A single add, remove or change or removing all items
+    // will trigger a sync for MULTI_DEVICE.
+    switch (data) {
+      case "modifyLogin":
+        subject = subject.QueryInterface(Ci.nsIArray).queryElementAt(1, Ci.nsILoginMetaInfo);
+        // Fall through.
+      case "addLogin":
+      case "removeLogin":
+        // Skip over Weave password/passphrase changes.
+        subject.QueryInterface(Ci.nsILoginMetaInfo).QueryInterface(Ci.nsILoginInfo);
+        if (Utils.getSyncCredentialsHosts().has(subject.hostname)) {
+          break;
+        }
+
+        this.score += SCORE_INCREMENT_XLARGE;
+        this._log.trace(data + ": " + subject.guid);
+        this.addChangedID(subject.guid);
+        break;
+      case "removeAllLogins":
+        this._log.trace(data);
+        this.score += SCORE_INCREMENT_XLARGE;
+        break;
+    }
+  },
+};
+
+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
new file mode 100644
index 000000000..9ceeb9ac6
--- /dev/null
+++ b/services/sync/modules/engines/prefs.js
@@ -0,0 +1,273 @@
+/* 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/. */
+
+this.EXPORTED_SYMBOLS = ['PrefsEngine', 'PrefRec'];
+
+var Cc = Components.classes;
+var Ci = Components.interfaces;
+var Cu = Components.utils;
+
+const PREF_SYNC_PREFS_PREFIX = "services.sync.prefs.sync.";
+
+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-common/utils.js");
+Cu.import("resource://gre/modules/LightweightThemeManager.jsm");
+Cu.import("resource://gre/modules/Preferences.jsm");
+
+const PREFS_GUID = CommonUtils.encodeBase64URL(Services.appinfo.ID);
+
+this.PrefRec = function PrefRec(collection, id) {
+  CryptoWrapper.call(this, collection, id);
+}
+PrefRec.prototype = {
+  __proto__: CryptoWrapper.prototype,
+  _logName: "Sync.Record.Pref",
+};
+
+Utils.deferGetSet(PrefRec, "cleartext", ["value"]);
+
+
+this.PrefsEngine = function PrefsEngine(service) {
+  SyncEngine.call(this, "Prefs", service);
+}
+PrefsEngine.prototype = {
+  __proto__: SyncEngine.prototype,
+  _storeObj: PrefStore,
+  _trackerObj: PrefTracker,
+  _recordObj: PrefRec,
+  version: 2,
+
+  syncPriority: 1,
+  allowSkippedRecord: false,
+
+  getChangedIDs: function () {
+    // No need for a proper timestamp (no conflict resolution needed).
+    let changedIDs = {};
+    if (this._tracker.modified)
+      changedIDs[PREFS_GUID] = 0;
+    return changedIDs;
+  },
+
+  _wipeClient: function () {
+    SyncEngine.prototype._wipeClient.call(this);
+    this.justWiped = true;
+  },
+
+  _reconcile: function (item) {
+    // Apply the incoming item if we don't care about the local data
+    if (this.justWiped) {
+      this.justWiped = false;
+      return true;
+    }
+    return SyncEngine.prototype._reconcile.call(this, item);
+  }
+};
+
+
+function PrefStore(name, engine) {
+  Store.call(this, name, engine);
+  Svc.Obs.add("profile-before-change", function () {
+    this.__prefs = null;
+  }, this);
+}
+PrefStore.prototype = {
+  __proto__: Store.prototype,
+
+ __prefs: null,
+  get _prefs() {
+    if (!this.__prefs) {
+      this.__prefs = new Preferences();
+    }
+    return this.__prefs;
+  },
+
+  _getSyncPrefs: function () {
+    let syncPrefs = Cc["@mozilla.org/preferences-service;1"]
+                      .getService(Ci.nsIPrefService)
+                      .getBranch(PREF_SYNC_PREFS_PREFIX)
+                      .getChildList("", {});
+    // Also sync preferences that determine which prefs get synced.
+    let controlPrefs = syncPrefs.map(pref => 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);
+  },
+
+  _getAllPrefs: function () {
+    let values = {};
+    for (let pref of 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;
+      }
+    }
+    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;
+
+    // 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));
+    for (let pref of prefs) {
+      if (!this._isSynced(pref)) {
+        continue;
+      }
+
+      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);
+            }
+          }
+      }
+    }
+
+    // Notify the lightweight theme manager if the selected theme has changed.
+    if (selectedThemeIDBefore != selectedThemeIDAfter) {
+      this._updateLightWeightTheme(selectedThemeIDAfter);
+    }
+  },
+
+  getAllIDs: function () {
+    /* We store all prefs in just one WBO, with just one GUID */
+    let allprefs = {};
+    allprefs[PREFS_GUID] = true;
+    return allprefs;
+  },
+
+  changeItemID: function (oldID, newID) {
+    this._log.trace("PrefStore GUID is constant!");
+  },
+
+  itemExists: function (id) {
+    return (id === PREFS_GUID);
+  },
+
+  createRecord: function (id, collection) {
+    let record = new PrefRec(collection, id);
+
+    if (id == PREFS_GUID) {
+      record.value = this._getAllPrefs();
+    } else {
+      record.deleted = true;
+    }
+
+    return record;
+  },
+
+  create: function (record) {
+    this._log.trace("Ignoring create request");
+  },
+
+  remove: function (record) {
+    this._log.trace("Ignoring remove request");
+  },
+
+  update: function (record) {
+    // Silently ignore pref updates that are for other apps.
+    if (record.id != PREFS_GUID)
+      return;
+
+    this._log.trace("Received pref updates, applying...");
+    this._setAllPrefs(record.value);
+  },
+
+  wipe: function () {
+    this._log.trace("Ignoring wipe request");
+  }
+};
+
+function PrefTracker(name, engine) {
+  Tracker.call(this, name, engine);
+  Svc.Obs.add("profile-before-change", this);
+  Svc.Obs.add("weave:engine:start-tracking", this);
+  Svc.Obs.add("weave:engine:stop-tracking", this);
+}
+PrefTracker.prototype = {
+  __proto__: Tracker.prototype,
+
+  get modified() {
+    return Svc.Prefs.get("engine.prefs.modified", false);
+  },
+  set modified(value) {
+    Svc.Prefs.set("engine.prefs.modified", value);
+  },
+
+  loadChangedIDs: function loadChangedIDs() {
+    // Don't read changed IDs from disk at start up.
+  },
+
+  clearChangedIDs: function clearChangedIDs() {
+    this.modified = false;
+  },
+
+ __prefs: null,
+  get _prefs() {
+    if (!this.__prefs) {
+      this.__prefs = new Preferences();
+    }
+    return this.__prefs;
+  },
+
+  startTracking: function () {
+    Services.prefs.addObserver("", this, false);
+  },
+
+  stopTracking: function () {
+    this.__prefs = null;
+    Services.prefs.removeObserver("", this);
+  },
+
+  observe: function (subject, topic, data) {
+    Tracker.prototype.observe.call(this, subject, topic, data);
+
+    switch (topic) {
+      case "profile-before-change":
+        this.stopTracking();
+        break;
+      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)) {
+          this.score += SCORE_INCREMENT_XLARGE;
+          this.modified = true;
+          this._log.trace("Preference " + data + " changed");
+        }
+        break;
+    }
+  }
+};
diff --git a/services/sync/modules/engines/tabs.js b/services/sync/modules/engines/tabs.js
new file mode 100644
index 000000000..45ece4a23
--- /dev/null
+++ b/services/sync/modules/engines/tabs.js
@@ -0,0 +1,393 @@
+/* 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/. */
+
+this.EXPORTED_SYMBOLS = ["TabEngine", "TabSetRecord"];
+
+var {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.
+
+Cu.import("resource://gre/modules/Preferences.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://services-sync/engines.js");
+Cu.import("resource://services-sync/engines/clients.js");
+Cu.import("resource://services-sync/record.js");
+Cu.import("resource://services-sync/util.js");
+Cu.import("resource://services-sync/constants.js");
+
+XPCOMUtils.defineLazyModuleGetter(this, "PrivateBrowsingUtils",
+  "resource://gre/modules/PrivateBrowsingUtils.jsm");
+
+this.TabSetRecord = function TabSetRecord(collection, id) {
+  CryptoWrapper.call(this, collection, id);
+}
+TabSetRecord.prototype = {
+  __proto__: CryptoWrapper.prototype,
+  _logName: "Sync.Record.Tabs",
+  ttl: TABS_TTL,
+};
+
+Utils.deferGetSet(TabSetRecord, "cleartext", ["clientName", "tabs"]);
+
+
+this.TabEngine = function TabEngine(service) {
+  SyncEngine.call(this, "Tabs", service);
+
+  // Reset the client on every startup so that we fetch recent tabs.
+  this._resetClient();
+}
+TabEngine.prototype = {
+  __proto__: SyncEngine.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,
+
+  getChangedIDs: function () {
+    // No need for a proper timestamp (no conflict resolution needed).
+    let changedIDs = {};
+    if (this._tracker.modified)
+      changedIDs[this.service.clientsEngine.localID] = 0;
+    return changedIDs;
+  },
+
+  // API for use by Sync UI code to give user choices of tabs to open.
+  getAllClients: function () {
+    return this._store._remoteClients;
+  },
+
+  getClientById: function (id) {
+    return this._store._remoteClients[id];
+  },
+
+  _resetClient: function () {
+    SyncEngine.prototype._resetClient.call(this);
+    this._store.wipe();
+    this._tracker.modified = true;
+    this.hasSyncedThisSession = false;
+  },
+
+  removeClientData: function () {
+    let url = this.engineURL + "/" + this.service.clientsEngine.localID;
+    this.service.resource(url).delete();
+  },
+
+  /**
+   * Return a Set of open URLs.
+   */
+  getOpenURLs: function () {
+    let urls = new Set();
+    for (let entry of this._store.getAllTabs()) {
+      urls.add(entry.urlHistory[0]);
+    }
+    return urls;
+  },
+
+  _reconcile: function (item) {
+    // Skip our own record.
+    // TabStore.itemExists tests only against our local client ID.
+    if (this._store.itemExists(item.id)) {
+      this._log.trace("Ignoring incoming tab item because of its id: " + item.id);
+      return false;
+    }
+
+    return SyncEngine.prototype._reconcile.call(this, item);
+  },
+
+  _syncFinish() {
+    this.hasSyncedThisSession = true;
+    return SyncEngine.prototype._syncFinish.call(this);
+  },
+};
+
+
+function TabStore(name, engine) {
+  Store.call(this, name, engine);
+}
+TabStore.prototype = {
+  __proto__: Store.prototype,
+
+  itemExists: function (id) {
+    return id == this.engine.service.clientsEngine.localID;
+  },
+
+  getWindowEnumerator: function () {
+    return Services.wm.getEnumerator("navigator:browser");
+  },
+
+  shouldSkipWindow: function (win) {
+    return win.closed ||
+           PrivateBrowsingUtils.isWindowPrivate(win);
+  },
+
+  getTabState: function (tab) {
+    return JSON.parse(Svc.Session.getTabState(tab));
+  },
+
+  getAllTabs: function (filter) {
+    let filteredUrls = new RegExp(Svc.Prefs.get("engine.tabs.filteredUrls"), "i");
+
+    let allTabs = [];
+
+    let winEnum = this.getWindowEnumerator();
+    while (winEnum.hasMoreElements()) {
+      let win = winEnum.getNext();
+      if (this.shouldSkipWindow(win)) {
+        continue;
+      }
+
+      for (let tab of win.gBrowser.tabs) {
+        let tabState = this.getTabState(tab);
+
+        // Make sure there are history entries to look at.
+        if (!tabState || !tabState.entries.length) {
+          continue;
+        }
+
+        let acceptable = !filter ? (url) => url :
+                                   (url) => url && !filteredUrls.test(url);
+
+        let entries = tabState.entries;
+        let index = tabState.index;
+        let current = entries[index - 1];
+
+        // We ignore the tab completely if the current entry url is
+        // not acceptable (we need something accurate to open).
+        if (!acceptable(current.url)) {
+          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.
+        let candidates = (entries.length == index) ?
+                         entries :
+                         entries.slice(0, index);
+
+        let urls = candidates.map((entry) => entry.url)
+                             .filter(acceptable)
+                             .reverse();                       // Because Sync puts current at index 0, and history after.
+
+        // Truncate if necessary.
+        if (urls.length > TAB_ENTRIES_LIMIT) {
+          urls.length = TAB_ENTRIES_LIMIT;
+        }
+
+        allTabs.push({
+          title: current.title || "",
+          urlHistory: urls,
+          icon: tabState.image ||
+                (tabState.attributes && tabState.attributes.image) ||
+                "",
+          lastUsed: Math.floor((tabState.lastAccessed || 0) / 1000),
+        });
+      }
+    }
+
+    return allTabs;
+  },
+
+  createRecord: function (id, collection) {
+    let record = new TabSetRecord(collection, id);
+    record.clientName = this.engine.service.clientsEngine.localName;
+
+    // Sort tabs in descending-used order to grab the most recently used
+    let tabs = this.getAllTabs(true).sort(function (a, b) {
+      return b.lastUsed - a.lastUsed;
+    });
+
+    // Figure out how many tabs we can pack into a payload. Starting with a 28KB
+    // payload, we can estimate various overheads from encryption/JSON/WBO.
+    let size = JSON.stringify(tabs).length;
+    let origLength = tabs.length;
+    const MAX_TAB_SIZE = 20000;
+    if (size > MAX_TAB_SIZE) {
+      // Estimate a little more than the direct fraction to maximize packing
+      let cutoff = Math.ceil(tabs.length * MAX_TAB_SIZE / size);
+      tabs = tabs.slice(0, cutoff + 1);
+
+      // Keep dropping off the last entry until the data fits
+      while (JSON.stringify(tabs).length > MAX_TAB_SIZE)
+        tabs.pop();
+    }
+
+    this._log.trace("Created tabs " + tabs.length + " of " + origLength);
+    tabs.forEach(function (tab) {
+      this._log.trace("Wrapping tab: " + JSON.stringify(tab));
+    }, this);
+
+    record.tabs = tabs;
+    return record;
+  },
+
+  getAllIDs: function () {
+    // Don't report any tabs if all windows are in private browsing for
+    // first syncs.
+    let ids = {};
+    let allWindowsArePrivate = false;
+    let wins = Services.wm.getEnumerator("navigator:browser");
+    while (wins.hasMoreElements()) {
+      if (PrivateBrowsingUtils.isWindowPrivate(wins.getNext())) {
+        // Ensure that at least there is a private window.
+        allWindowsArePrivate = true;
+      } else {
+        // If there is a not private windown then finish and continue.
+        allWindowsArePrivate = false;
+        break;
+      }
+    }
+
+    if (allWindowsArePrivate &&
+        !PrivateBrowsingUtils.permanentPrivateBrowsing) {
+      return ids;
+    }
+
+    ids[this.engine.service.clientsEngine.localID] = true;
+    return ids;
+  },
+
+  wipe: function () {
+    this._remoteClients = {};
+  },
+
+  create: function (record) {
+    this._log.debug("Adding remote tabs from " + record.clientName);
+    this._remoteClients[record.id] = Object.assign({}, record.cleartext, {
+      lastModified: record.modified
+    });
+  },
+
+  update: function (record) {
+    this._log.trace("Ignoring tab updates as local ones win");
+  },
+};
+
+
+function TabTracker(name, engine) {
+  Tracker.call(this, name, engine);
+  Svc.Obs.add("weave:engine:start-tracking", this);
+  Svc.Obs.add("weave:engine:stop-tracking", this);
+
+  // Make sure "this" pointer is always set correctly for event listeners.
+  this.onTab = Utils.bind2(this, this.onTab);
+  this._unregisterListeners = Utils.bind2(this, this._unregisterListeners);
+}
+TabTracker.prototype = {
+  __proto__: Tracker.prototype,
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver]),
+
+  loadChangedIDs: function () {
+    // Don't read changed IDs from disk at start up.
+  },
+
+  clearChangedIDs: function () {
+    this.modified = false;
+  },
+
+  _topics: ["pageshow", "TabOpen", "TabClose", "TabSelect"],
+
+  _registerListenersForWindow: function (window) {
+    this._log.trace("Registering tab listeners in window");
+    for (let topic of 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) {
+    this._unregisterListenersForWindow(event.target);
+  },
+
+  _unregisterListenersForWindow: function (window) {
+    this._log.trace("Removing tab listeners in window");
+    window.removeEventListener("unload", this._unregisterListeners, false);
+    for (let topic of this._topics) {
+      window.removeEventListener(topic, this.onTab, false);
+    }
+    if (window.gBrowser) {
+      window.gBrowser.removeProgressListener(this);
+    }
+  },
+
+  startTracking: function () {
+    Svc.Obs.add("domwindowopened", this);
+    let wins = Services.wm.getEnumerator("navigator:browser");
+    while (wins.hasMoreElements()) {
+      this._registerListenersForWindow(wins.getNext());
+    }
+  },
+
+  stopTracking: function () {
+    Svc.Obs.remove("domwindowopened", this);
+    let wins = Services.wm.getEnumerator("navigator:browser");
+    while (wins.hasMoreElements()) {
+      this._unregisterListenersForWindow(wins.getNext());
+    }
+  },
+
+  observe: function (subject, topic, data) {
+    Tracker.prototype.observe.call(this, subject, topic, data);
+
+    switch (topic) {
+      case "domwindowopened":
+        let onLoad = () => {
+          subject.removeEventListener("load", onLoad, false);
+          // Only register after the window is done loading to avoid unloads.
+          this._registerListenersForWindow(subject);
+        };
+
+        // Add tab listeners now that a window has opened.
+        subject.addEventListener("load", onLoad, false);
+        break;
+    }
+  },
+
+  onTab: function (event) {
+    if (event.originalTarget.linkedBrowser) {
+      let browser = event.originalTarget.linkedBrowser;
+      if (PrivateBrowsingUtils.isBrowserPrivate(browser) &&
+          !PrivateBrowsingUtils.permanentPrivateBrowsing) {
+        this._log.trace("Ignoring tab event from private browsing.");
+        return;
+      }
+    }
+
+    this._log.trace("onTab event: " + event.type);
+    this.modified = true;
+
+    // For page shows, bump the score 10% of the time, emulating a partial
+    // score. We don't want to sync too frequently. For all other page
+    // events, always bump the score.
+    if (event.type != "pageshow" || Math.random() < .1) {
+      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;
+    }
+  },
+};