Move WebExtensions enabled Add-ons Manager

1 files changed, 9305 insertions, 0 deletions

diff --git a/toolkit/mozapps/webextensions/internal/XPIProvider.jsm b/toolkit/mozapps/webextensions/internal/XPIProvider.jsm
new file mode 100644
index 000000000..87e09cef1
--- /dev/null
+++ b/toolkit/mozapps/webextensions/internal/XPIProvider.jsm
@@ -0,0 +1,9305 @@
+ /* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+const Cu = Components.utils;
+
+this.EXPORTED_SYMBOLS = ["XPIProvider"];
+
+const CONSTANTS = {};
+Cu.import("resource://gre/modules/addons/AddonConstants.jsm", CONSTANTS);
+const { ADDON_SIGNING, REQUIRE_SIGNING } = CONSTANTS
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/AddonManager.jsm");
+Cu.import("resource://gre/modules/Preferences.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "AddonRepository",
+                                  "resource://gre/modules/addons/AddonRepository.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "ChromeManifestParser",
+                                  "resource://gre/modules/ChromeManifestParser.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "LightweightThemeManager",
+                                  "resource://gre/modules/LightweightThemeManager.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "ExtensionData",
+                                  "resource://gre/modules/Extension.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "ExtensionManagement",
+                                  "resource://gre/modules/ExtensionManagement.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Locale",
+                                  "resource://gre/modules/Locale.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
+                                  "resource://gre/modules/FileUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "ZipUtils",
+                                  "resource://gre/modules/ZipUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
+                                  "resource://gre/modules/NetUtil.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "PermissionsUtils",
+                                  "resource://gre/modules/PermissionsUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Promise",
+                                  "resource://gre/modules/Promise.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+                                  "resource://gre/modules/Task.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "OS",
+                                  "resource://gre/modules/osfile.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "BrowserToolboxProcess",
+                                  "resource://devtools/client/framework/ToolboxProcess.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "ConsoleAPI",
+                                  "resource://gre/modules/Console.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "ProductAddonChecker",
+                                  "resource://gre/modules/addons/ProductAddonChecker.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "UpdateUtils",
+                                  "resource://gre/modules/UpdateUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "AppConstants",
+                                  "resource://gre/modules/AppConstants.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "isAddonPartOfE10SRollout",
+                                  "resource://gre/modules/addons/E10SAddonsRollout.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "LegacyExtensionsUtils",
+                                  "resource://gre/modules/LegacyExtensionsUtils.jsm");
+
+XPCOMUtils.defineLazyServiceGetter(this, "Blocklist",
+                                   "@mozilla.org/extensions/blocklist;1",
+                                   Ci.nsIBlocklistService);
+XPCOMUtils.defineLazyServiceGetter(this,
+                                   "ChromeRegistry",
+                                   "@mozilla.org/chrome/chrome-registry;1",
+                                   "nsIChromeRegistry");
+XPCOMUtils.defineLazyServiceGetter(this,
+                                   "ResProtocolHandler",
+                                   "@mozilla.org/network/protocol;1?name=resource",
+                                   "nsIResProtocolHandler");
+XPCOMUtils.defineLazyServiceGetter(this,
+                                   "AddonPolicyService",
+                                   "@mozilla.org/addons/policy-service;1",
+                                   "nsIAddonPolicyService");
+XPCOMUtils.defineLazyServiceGetter(this,
+                                   "AddonPathService",
+                                   "@mozilla.org/addon-path-service;1",
+                                   "amIAddonPathService");
+
+XPCOMUtils.defineLazyGetter(this, "CertUtils", function() {
+  let certUtils = {};
+  Components.utils.import("resource://gre/modules/CertUtils.jsm", certUtils);
+  return certUtils;
+});
+
+Cu.importGlobalProperties(["URL"]);
+
+const nsIFile = Components.Constructor("@mozilla.org/file/local;1", "nsIFile",
+                                       "initWithPath");
+
+const PREF_DB_SCHEMA                  = "extensions.databaseSchema";
+const PREF_INSTALL_CACHE              = "extensions.installCache";
+const PREF_XPI_STATE                  = "extensions.xpiState";
+const PREF_BOOTSTRAP_ADDONS           = "extensions.bootstrappedAddons";
+const PREF_PENDING_OPERATIONS         = "extensions.pendingOperations";
+const PREF_EM_DSS_ENABLED             = "extensions.dss.enabled";
+const PREF_DSS_SWITCHPENDING          = "extensions.dss.switchPending";
+const PREF_DSS_SKIN_TO_SELECT         = "extensions.lastSelectedSkin";
+const PREF_GENERAL_SKINS_SELECTEDSKIN = "general.skins.selectedSkin";
+const PREF_EM_UPDATE_URL              = "extensions.update.url";
+const PREF_EM_UPDATE_BACKGROUND_URL   = "extensions.update.background.url";
+const PREF_EM_ENABLED_ADDONS          = "extensions.enabledAddons";
+const PREF_EM_EXTENSION_FORMAT        = "extensions.";
+const PREF_EM_ENABLED_SCOPES          = "extensions.enabledScopes";
+const PREF_EM_SHOW_MISMATCH_UI        = "extensions.showMismatchUI";
+const PREF_XPI_ENABLED                = "xpinstall.enabled";
+const PREF_XPI_WHITELIST_REQUIRED     = "xpinstall.whitelist.required";
+const PREF_XPI_DIRECT_WHITELISTED     = "xpinstall.whitelist.directRequest";
+const PREF_XPI_FILE_WHITELISTED       = "xpinstall.whitelist.fileRequest";
+// xpinstall.signatures.required only supported in dev builds
+const PREF_XPI_SIGNATURES_REQUIRED    = "xpinstall.signatures.required";
+const PREF_XPI_SIGNATURES_DEV_ROOT    = "xpinstall.signatures.dev-root";
+const PREF_XPI_PERMISSIONS_BRANCH     = "xpinstall.";
+const PREF_XPI_UNPACK                 = "extensions.alwaysUnpack";
+const PREF_INSTALL_REQUIREBUILTINCERTS = "extensions.install.requireBuiltInCerts";
+const PREF_INSTALL_REQUIRESECUREORIGIN = "extensions.install.requireSecureOrigin";
+const PREF_INSTALL_DISTRO_ADDONS      = "extensions.installDistroAddons";
+const PREF_BRANCH_INSTALLED_ADDON     = "extensions.installedDistroAddon.";
+const PREF_INTERPOSITION_ENABLED      = "extensions.interposition.enabled";
+const PREF_SYSTEM_ADDON_SET           = "extensions.systemAddonSet";
+const PREF_SYSTEM_ADDON_UPDATE_URL    = "extensions.systemAddon.update.url";
+const PREF_E10S_BLOCK_ENABLE          = "extensions.e10sBlocksEnabling";
+const PREF_E10S_ADDON_BLOCKLIST       = "extensions.e10s.rollout.blocklist";
+const PREF_E10S_ADDON_POLICY          = "extensions.e10s.rollout.policy";
+const PREF_E10S_HAS_NONEXEMPT_ADDON   = "extensions.e10s.rollout.hasAddon";
+
+const PREF_EM_MIN_COMPAT_APP_VERSION      = "extensions.minCompatibleAppVersion";
+const PREF_EM_MIN_COMPAT_PLATFORM_VERSION = "extensions.minCompatiblePlatformVersion";
+
+const PREF_CHECKCOMAT_THEMEOVERRIDE   = "extensions.checkCompatibility.temporaryThemeOverride_minAppVersion";
+
+const PREF_EM_HOTFIX_ID               = "extensions.hotfix.id";
+const PREF_EM_CERT_CHECKATTRIBUTES    = "extensions.hotfix.cert.checkAttributes";
+const PREF_EM_HOTFIX_CERTS            = "extensions.hotfix.certs.";
+
+const URI_EXTENSION_UPDATE_DIALOG     = "chrome://mozapps/content/extensions/update.xul";
+const URI_EXTENSION_STRINGS           = "chrome://mozapps/locale/extensions/extensions.properties";
+
+const STRING_TYPE_NAME                = "type.%ID%.name";
+
+const DIR_EXTENSIONS                  = "extensions";
+const DIR_SYSTEM_ADDONS               = "features";
+const DIR_STAGE                       = "staged";
+const DIR_TRASH                       = "trash";
+
+const FILE_DATABASE                   = "extensions.json";
+const FILE_OLD_CACHE                  = "extensions.cache";
+const FILE_RDF_MANIFEST               = "install.rdf";
+const FILE_WEB_MANIFEST               = "manifest.json";
+const FILE_XPI_ADDONS_LIST            = "extensions.ini";
+
+const KEY_PROFILEDIR                  = "ProfD";
+const KEY_ADDON_APP_DIR               = "XREAddonAppDir";
+const KEY_TEMPDIR                     = "TmpD";
+const KEY_APP_DISTRIBUTION            = "XREAppDist";
+const KEY_APP_FEATURES                = "XREAppFeat";
+
+const KEY_APP_PROFILE                 = "app-profile";
+const KEY_APP_SYSTEM_ADDONS           = "app-system-addons";
+const KEY_APP_SYSTEM_DEFAULTS         = "app-system-defaults";
+const KEY_APP_GLOBAL                  = "app-global";
+const KEY_APP_SYSTEM_LOCAL            = "app-system-local";
+const KEY_APP_SYSTEM_SHARE            = "app-system-share";
+const KEY_APP_SYSTEM_USER             = "app-system-user";
+const KEY_APP_TEMPORARY               = "app-temporary";
+
+const NOTIFICATION_FLUSH_PERMISSIONS  = "flush-pending-permissions";
+const XPI_PERMISSION                  = "install";
+
+const RDFURI_INSTALL_MANIFEST_ROOT    = "urn:mozilla:install-manifest";
+const PREFIX_NS_EM                    = "http://www.mozilla.org/2004/em-rdf#";
+
+const TOOLKIT_ID                      = "toolkit@mozilla.org";
+
+const XPI_SIGNATURE_CHECK_PERIOD      = 24 * 60 * 60;
+
+XPCOMUtils.defineConstant(this, "DB_SCHEMA", 19);
+
+const NOTIFICATION_TOOLBOXPROCESS_LOADED      = "ToolboxProcessLoaded";
+
+// Properties that exist in the install manifest
+const PROP_METADATA      = ["id", "version", "type", "internalName", "updateURL",
+                            "updateKey", "optionsURL", "optionsType", "aboutURL",
+                            "iconURL", "icon64URL"];
+const PROP_LOCALE_SINGLE = ["name", "description", "creator", "homepageURL"];
+const PROP_LOCALE_MULTI  = ["developers", "translators", "contributors"];
+const PROP_TARGETAPP     = ["id", "minVersion", "maxVersion"];
+
+// Properties to cache and reload when an addon installation is pending
+const PENDING_INSTALL_METADATA =
+    ["syncGUID", "targetApplications", "userDisabled", "softDisabled",
+     "existingAddonID", "sourceURI", "releaseNotesURI", "installDate",
+     "updateDate", "applyBackgroundUpdates", "compatibilityOverrides"];
+
+// Note: When adding/changing/removing items here, remember to change the
+// DB schema version to ensure changes are picked up ASAP.
+const STATIC_BLOCKLIST_PATTERNS = [
+  { creator: "Mozilla Corp.",
+    level: Blocklist.STATE_BLOCKED,
+    blockID: "i162" },
+  { creator: "Mozilla.org",
+    level: Blocklist.STATE_BLOCKED,
+    blockID: "i162" }
+];
+
+
+const BOOTSTRAP_REASONS = {
+  APP_STARTUP     : 1,
+  APP_SHUTDOWN    : 2,
+  ADDON_ENABLE    : 3,
+  ADDON_DISABLE   : 4,
+  ADDON_INSTALL   : 5,
+  ADDON_UNINSTALL : 6,
+  ADDON_UPGRADE   : 7,
+  ADDON_DOWNGRADE : 8
+};
+
+// Map new string type identifiers to old style nsIUpdateItem types
+const TYPES = {
+  extension: 2,
+  theme: 4,
+  locale: 8,
+  multipackage: 32,
+  dictionary: 64,
+  experiment: 128,
+};
+
+if (!AppConstants.RELEASE_OR_BETA)
+  TYPES.apiextension = 256;
+
+// Some add-on types that we track internally are presented as other types
+// externally
+const TYPE_ALIASES = {
+  "webextension": "extension",
+  "apiextension": "extension",
+};
+
+const CHROME_TYPES = new Set([
+  "extension",
+  "locale",
+  "experiment",
+]);
+
+const RESTARTLESS_TYPES = new Set([
+  "webextension",
+  "dictionary",
+  "experiment",
+  "locale",
+  "apiextension",
+]);
+
+const SIGNED_TYPES = new Set([
+  "webextension",
+  "extension",
+  "experiment",
+  "apiextension",
+]);
+
+// This is a random number array that can be used as "salt" when generating
+// an automatic ID based on the directory path of an add-on. It will prevent
+// someone from creating an ID for a permanent add-on that could be replaced
+// by a temporary add-on (because that would be confusing, I guess).
+const TEMP_INSTALL_ID_GEN_SESSION =
+  new Uint8Array(Float64Array.of(Math.random()).buffer);
+
+// Whether add-on signing is required.
+function mustSign(aType) {
+  if (!SIGNED_TYPES.has(aType))
+    return false;
+  return REQUIRE_SIGNING || Preferences.get(PREF_XPI_SIGNATURES_REQUIRED, false);
+}
+
+// Keep track of where we are in startup for telemetry
+// event happened during XPIDatabase.startup()
+const XPI_STARTING = "XPIStarting";
+// event happened after startup() but before the final-ui-startup event
+const XPI_BEFORE_UI_STARTUP = "BeforeFinalUIStartup";
+// event happened after final-ui-startup
+const XPI_AFTER_UI_STARTUP = "AfterFinalUIStartup";
+
+const COMPATIBLE_BY_DEFAULT_TYPES = {
+  extension: true,
+  dictionary: true
+};
+
+const MSG_JAR_FLUSH = "AddonJarFlush";
+const MSG_MESSAGE_MANAGER_CACHES_FLUSH = "AddonMessageManagerCachesFlush";
+
+var gGlobalScope = this;
+
+/**
+ * Valid IDs fit this pattern.
+ */
+var gIDTest = /^(\{[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}\}|[a-z0-9-\._]*\@[a-z0-9-\._]+)$/i;
+
+Cu.import("resource://gre/modules/Log.jsm");
+const LOGGER_ID = "addons.xpi";
+
+// Create a new logger for use by all objects in this Addons XPI Provider module
+// (Requires AddonManager.jsm)
+var logger = Log.repository.getLogger(LOGGER_ID);
+
+const LAZY_OBJECTS = ["XPIDatabase", "XPIDatabaseReconcile"];
+/* globals XPIDatabase, XPIDatabaseReconcile*/
+
+var gLazyObjectsLoaded = false;
+
+function loadLazyObjects() {
+  let uri = "resource://gre/modules/addons/XPIProviderUtils.js";
+  let scope = Cu.Sandbox(Services.scriptSecurityManager.getSystemPrincipal(), {
+    sandboxName: uri,
+    wantGlobalProperties: ["TextDecoder"],
+  });
+
+  let shared = {
+    ADDON_SIGNING,
+    SIGNED_TYPES,
+    BOOTSTRAP_REASONS,
+    DB_SCHEMA,
+    AddonInternal,
+    XPIProvider,
+    XPIStates,
+    syncLoadManifestFromFile,
+    isUsableAddon,
+    recordAddonTelemetry,
+    applyBlocklistChanges,
+    flushChromeCaches,
+    canRunInSafeMode,
+  }
+
+  for (let key of Object.keys(shared))
+    scope[key] = shared[key];
+
+  Services.scriptloader.loadSubScript(uri, scope);
+
+  for (let name of LAZY_OBJECTS) {
+    delete gGlobalScope[name];
+    gGlobalScope[name] = scope[name];
+  }
+  gLazyObjectsLoaded = true;
+  return scope;
+}
+
+LAZY_OBJECTS.forEach(name => {
+  Object.defineProperty(gGlobalScope, name, {
+    get: function() {
+      let objs = loadLazyObjects();
+      return objs[name];
+    },
+    configurable: true
+  });
+});
+
+
+// Behaves like Promise.all except waits for all promises to resolve/reject
+// before resolving/rejecting itself
+function waitForAllPromises(promises) {
+  return new Promise((resolve, reject) => {
+    let shouldReject = false;
+    let rejectValue = null;
+
+    let newPromises = promises.map(
+      p => p.catch(value => {
+        shouldReject = true;
+        rejectValue = value;
+      })
+    );
+    Promise.all(newPromises)
+           .then((results) => shouldReject ? reject(rejectValue) : resolve(results));
+  });
+}
+
+function findMatchingStaticBlocklistItem(aAddon) {
+  for (let item of STATIC_BLOCKLIST_PATTERNS) {
+    if ("creator" in item && typeof item.creator == "string") {
+      if ((aAddon.defaultLocale && aAddon.defaultLocale.creator == item.creator) ||
+          (aAddon.selectedLocale && aAddon.selectedLocale.creator == item.creator)) {
+        return item;
+      }
+    }
+  }
+  return null;
+}
+
+/**
+ * Converts an iterable of addon objects into a map with the add-on's ID as key.
+ */
+function addonMap(addons) {
+  return new Map(addons.map(a => [a.id, a]));
+}
+
+/**
+ * Sets permissions on a file
+ *
+ * @param  aFile
+ *         The file or directory to operate on.
+ * @param  aPermissions
+ *         The permisions to set
+ */
+function setFilePermissions(aFile, aPermissions) {
+  try {
+    aFile.permissions = aPermissions;
+  }
+  catch (e) {
+    logger.warn("Failed to set permissions " + aPermissions.toString(8) + " on " +
+         aFile.path, e);
+  }
+}
+
+/**
+ * Write a given string to a file
+ *
+ * @param  file
+ *         The nsIFile instance to write into
+ * @param  string
+ *         The string to write
+ */
+function writeStringToFile(file, string) {
+  let stream = Cc["@mozilla.org/network/file-output-stream;1"].
+               createInstance(Ci.nsIFileOutputStream);
+  let converter = Cc["@mozilla.org/intl/converter-output-stream;1"].
+                  createInstance(Ci.nsIConverterOutputStream);
+
+  try {
+    stream.init(file, FileUtils.MODE_WRONLY | FileUtils.MODE_CREATE |
+                            FileUtils.MODE_TRUNCATE, FileUtils.PERMS_FILE,
+                           0);
+    converter.init(stream, "UTF-8", 0, 0x0000);
+    converter.writeString(string);
+  }
+  finally {
+    converter.close();
+    stream.close();
+  }
+}
+
+/**
+ * A safe way to install a file or the contents of a directory to a new
+ * directory. The file or directory is moved or copied recursively and if
+ * anything fails an attempt is made to rollback the entire operation. The
+ * operation may also be rolled back to its original state after it has
+ * completed by calling the rollback method.
+ *
+ * Operations can be chained. Calling move or copy multiple times will remember
+ * the whole set and if one fails all of the operations will be rolled back.
+ */
+function SafeInstallOperation() {
+  this._installedFiles = [];
+  this._createdDirs = [];
+}
+
+SafeInstallOperation.prototype = {
+  _installedFiles: null,
+  _createdDirs: null,
+
+  _installFile: function(aFile, aTargetDirectory, aCopy) {
+    let oldFile = aCopy ? null : aFile.clone();
+    let newFile = aFile.clone();
+    try {
+      if (aCopy) {
+        newFile.copyTo(aTargetDirectory, null);
+        // copyTo does not update the nsIFile with the new.
+        newFile = aTargetDirectory.clone();
+        newFile.append(aFile.leafName);
+        // Windows roaming profiles won't properly sync directories if a new file
+        // has an older lastModifiedTime than a previous file, so update.
+        newFile.lastModifiedTime = Date.now();
+      }
+      else {
+        newFile.moveTo(aTargetDirectory, null);
+      }
+    }
+    catch (e) {
+      logger.error("Failed to " + (aCopy ? "copy" : "move") + " file " + aFile.path +
+            " to " + aTargetDirectory.path, e);
+      throw e;
+    }
+    this._installedFiles.push({ oldFile: oldFile, newFile: newFile });
+  },
+
+  _installDirectory: function(aDirectory, aTargetDirectory, aCopy) {
+    if (aDirectory.contains(aTargetDirectory)) {
+      let err = new Error(`Not installing ${aDirectory} into its own descendent ${aTargetDirectory}`);
+      logger.error(err);
+      throw err;
+    }
+
+    let newDir = aTargetDirectory.clone();
+    newDir.append(aDirectory.leafName);
+    try {
+      newDir.create(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+    }
+    catch (e) {
+      logger.error("Failed to create directory " + newDir.path, e);
+      throw e;
+    }
+    this._createdDirs.push(newDir);
+
+    // Use a snapshot of the directory contents to avoid possible issues with
+    // iterating over a directory while removing files from it (the YAFFS2
+    // embedded filesystem has this issue, see bug 772238), and to remove
+    // normal files before their resource forks on OSX (see bug 733436).
+    let entries = getDirectoryEntries(aDirectory, true);
+    for (let entry of entries) {
+      try {
+        this._installDirEntry(entry, newDir, aCopy);
+      }
+      catch (e) {
+        logger.error("Failed to " + (aCopy ? "copy" : "move") + " entry " +
+                     entry.path, e);
+        throw e;
+      }
+    }
+
+    // If this is only a copy operation then there is nothing else to do
+    if (aCopy)
+      return;
+
+    // The directory should be empty by this point. If it isn't this will throw
+    // and all of the operations will be rolled back
+    try {
+      setFilePermissions(aDirectory, FileUtils.PERMS_DIRECTORY);
+      aDirectory.remove(false);
+    }
+    catch (e) {
+      logger.error("Failed to remove directory " + aDirectory.path, e);
+      throw e;
+    }
+
+    // Note we put the directory move in after all the file moves so the
+    // directory is recreated before all the files are moved back
+    this._installedFiles.push({ oldFile: aDirectory, newFile: newDir });
+  },
+
+  _installDirEntry: function(aDirEntry, aTargetDirectory, aCopy) {
+    let isDir = null;
+
+    try {
+      isDir = aDirEntry.isDirectory() && !aDirEntry.isSymlink();
+    }
+    catch (e) {
+      // If the file has already gone away then don't worry about it, this can
+      // happen on OSX where the resource fork is automatically moved with the
+      // data fork for the file. See bug 733436.
+      if (e.result == Cr.NS_ERROR_FILE_TARGET_DOES_NOT_EXIST)
+        return;
+
+      logger.error("Failure " + (aCopy ? "copying" : "moving") + " " + aDirEntry.path +
+            " to " + aTargetDirectory.path);
+      throw e;
+    }
+
+    try {
+      if (isDir)
+        this._installDirectory(aDirEntry, aTargetDirectory, aCopy);
+      else
+        this._installFile(aDirEntry, aTargetDirectory, aCopy);
+    }
+    catch (e) {
+      logger.error("Failure " + (aCopy ? "copying" : "moving") + " " + aDirEntry.path +
+            " to " + aTargetDirectory.path);
+      throw e;
+    }
+  },
+
+  /**
+   * Moves a file or directory into a new directory. If an error occurs then all
+   * files that have been moved will be moved back to their original location.
+   *
+   * @param  aFile
+   *         The file or directory to be moved.
+   * @param  aTargetDirectory
+   *         The directory to move into, this is expected to be an empty
+   *         directory.
+   */
+  moveUnder: function(aFile, aTargetDirectory) {
+    try {
+      this._installDirEntry(aFile, aTargetDirectory, false);
+    }
+    catch (e) {
+      this.rollback();
+      throw e;
+    }
+  },
+
+  /**
+   * Renames a file to a new location.  If an error occurs then all
+   * files that have been moved will be moved back to their original location.
+   *
+   * @param  aOldLocation
+   *         The old location of the file.
+   * @param  aNewLocation
+   *         The new location of the file.
+   */
+  moveTo: function(aOldLocation, aNewLocation) {
+    try {
+      let oldFile = aOldLocation.clone(), newFile = aNewLocation.clone();
+      oldFile.moveTo(newFile.parent, newFile.leafName);
+      this._installedFiles.push({ oldFile: oldFile, newFile: newFile, isMoveTo: true});
+    }
+    catch (e) {
+      this.rollback();
+      throw e;
+    }
+  },
+
+  /**
+   * Copies a file or directory into a new directory. If an error occurs then
+   * all new files that have been created will be removed.
+   *
+   * @param  aFile
+   *         The file or directory to be copied.
+   * @param  aTargetDirectory
+   *         The directory to copy into, this is expected to be an empty
+   *         directory.
+   */
+  copy: function(aFile, aTargetDirectory) {
+    try {
+      this._installDirEntry(aFile, aTargetDirectory, true);
+    }
+    catch (e) {
+      this.rollback();
+      throw e;
+    }
+  },
+
+  /**
+   * Rolls back all the moves that this operation performed. If an exception
+   * occurs here then both old and new directories are left in an indeterminate
+   * state
+   */
+  rollback: function() {
+    while (this._installedFiles.length > 0) {
+      let move = this._installedFiles.pop();
+      if (move.isMoveTo) {
+        move.newFile.moveTo(move.oldDir.parent, move.oldDir.leafName);
+      }
+      else if (move.newFile.isDirectory() && !move.newFile.isSymlink()) {
+        let oldDir = move.oldFile.parent.clone();
+        oldDir.append(move.oldFile.leafName);
+        oldDir.create(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+      }
+      else if (!move.oldFile) {
+        // No old file means this was a copied file
+        move.newFile.remove(true);
+      }
+      else {
+        move.newFile.moveTo(move.oldFile.parent, null);
+      }
+    }
+
+    while (this._createdDirs.length > 0)
+      recursiveRemove(this._createdDirs.pop());
+  }
+};
+
+/**
+ * Sets the userDisabled and softDisabled properties of an add-on based on what
+ * values those properties had for a previous instance of the add-on. The
+ * previous instance may be a previous install or in the case of an application
+ * version change the same add-on.
+ *
+ * NOTE: this may modify aNewAddon in place; callers should save the database if
+ * necessary
+ *
+ * @param  aOldAddon
+ *         The previous instance of the add-on
+ * @param  aNewAddon
+ *         The new instance of the add-on
+ * @param  aAppVersion
+ *         The optional application version to use when checking the blocklist
+ *         or undefined to use the current application
+ * @param  aPlatformVersion
+ *         The optional platform version to use when checking the blocklist or
+ *         undefined to use the current platform
+ */
+function applyBlocklistChanges(aOldAddon, aNewAddon, aOldAppVersion,
+                               aOldPlatformVersion) {
+  // Copy the properties by default
+  aNewAddon.userDisabled = aOldAddon.userDisabled;
+  aNewAddon.softDisabled = aOldAddon.softDisabled;
+
+  let oldBlocklistState = Blocklist.getAddonBlocklistState(aOldAddon.wrapper,
+                                                           aOldAppVersion,
+                                                           aOldPlatformVersion);
+  let newBlocklistState = Blocklist.getAddonBlocklistState(aNewAddon.wrapper);
+
+  // If the blocklist state hasn't changed then the properties don't need to
+  // change
+  if (newBlocklistState == oldBlocklistState)
+    return;
+
+  if (newBlocklistState == Blocklist.STATE_SOFTBLOCKED) {
+    if (aNewAddon.type != "theme") {
+      // The add-on has become softblocked, set softDisabled if it isn't already
+      // userDisabled
+      aNewAddon.softDisabled = !aNewAddon.userDisabled;
+    }
+    else {
+      // Themes just get userDisabled to switch back to the default theme
+      aNewAddon.userDisabled = true;
+    }
+  }
+  else {
+    // If the new add-on is not softblocked then it cannot be softDisabled
+    aNewAddon.softDisabled = false;
+  }
+}
+
+/**
+ * Evaluates whether an add-on is allowed to run in safe mode.
+ *
+ * @param  aAddon
+ *         The add-on to check
+ * @return true if the add-on should run in safe mode
+ */
+function canRunInSafeMode(aAddon) {
+  // Even though the updated system add-ons aren't generally run in safe mode we
+  // include them here so their uninstall functions get called when switching
+  // back to the default set.
+
+  // TODO product should make the call about temporary add-ons running
+  // in safe mode. assuming for now that they are.
+  if (aAddon._installLocation.name == KEY_APP_TEMPORARY)
+    return true;
+
+  return aAddon._installLocation.name == KEY_APP_SYSTEM_DEFAULTS ||
+         aAddon._installLocation.name == KEY_APP_SYSTEM_ADDONS;
+}
+
+/**
+ * Calculates whether an add-on should be appDisabled or not.
+ *
+ * @param  aAddon
+ *         The add-on to check
+ * @return true if the add-on should not be appDisabled
+ */
+function isUsableAddon(aAddon) {
+  // Hack to ensure the default theme is always usable
+  if (aAddon.type == "theme" && aAddon.internalName == XPIProvider.defaultSkin)
+    return true;
+
+  if (mustSign(aAddon.type) && !aAddon.isCorrectlySigned) {
+    logger.warn(`Add-on ${aAddon.id} is not correctly signed.`);
+    return false;
+  }
+
+  if (aAddon.blocklistState == Blocklist.STATE_BLOCKED) {
+    logger.warn(`Add-on ${aAddon.id} is blocklisted.`);
+    return false;
+  }
+
+  // Experiments are installed through an external mechanism that
+  // limits target audience to compatible clients. We trust it knows what
+  // it's doing and skip compatibility checks.
+  //
+  // This decision does forfeit defense in depth. If the experiments system
+  // is ever wrong about targeting an add-on to a specific application
+  // or platform, the client will likely see errors.
+  if (aAddon.type == "experiment")
+    return true;
+
+  if (AddonManager.checkUpdateSecurity && !aAddon.providesUpdatesSecurely) {
+    logger.warn(`Updates for add-on ${aAddon.id} must be provided over HTTPS.`);
+    return false;
+  }
+
+
+  if (!aAddon.isPlatformCompatible) {
+    logger.warn(`Add-on ${aAddon.id} is not compatible with platform.`);
+    return false;
+  }
+
+  if (aAddon.dependencies.length) {
+    let isActive = id => {
+      let active = XPIProvider.activeAddons.get(id);
+      return active && !active.disable;
+    };
+
+    if (aAddon.dependencies.some(id => !isActive(id)))
+      return false;
+  }
+
+  if (AddonManager.checkCompatibility) {
+    if (!aAddon.isCompatible) {
+      logger.warn(`Add-on ${aAddon.id} is not compatible with application version.`);
+      return false;
+    }
+  }
+  else {
+    let app = aAddon.matchingTargetApplication;
+    if (!app) {
+      logger.warn(`Add-on ${aAddon.id} is not compatible with target application.`);
+      return false;
+    }
+
+    // XXX Temporary solution to let applications opt-in to make themes safer
+    //     following significant UI changes even if checkCompatibility=false has
+    //     been set, until we get bug 962001.
+    if (aAddon.type == "theme" && app.id == Services.appinfo.ID) {
+      try {
+        let minCompatVersion = Services.prefs.getCharPref(PREF_CHECKCOMAT_THEMEOVERRIDE);
+        if (minCompatVersion &&
+            Services.vc.compare(minCompatVersion, app.maxVersion) > 0) {
+          logger.warn(`Theme ${aAddon.id} is not compatible with application version.`);
+          return false;
+        }
+      } catch (e) {}
+    }
+  }
+
+  return true;
+}
+
+XPCOMUtils.defineLazyServiceGetter(this, "gRDF", "@mozilla.org/rdf/rdf-service;1",
+                                   Ci.nsIRDFService);
+
+function EM_R(aProperty) {
+  return gRDF.GetResource(PREFIX_NS_EM + aProperty);
+}
+
+function createAddonDetails(id, aAddon) {
+  return {
+    id: id || aAddon.id,
+    type: aAddon.type,
+    version: aAddon.version,
+    multiprocessCompatible: aAddon.multiprocessCompatible,
+    mpcOptedOut: aAddon.mpcOptedOut,
+    runInSafeMode: aAddon.runInSafeMode,
+    dependencies: aAddon.dependencies,
+    hasEmbeddedWebExtension: aAddon.hasEmbeddedWebExtension,
+  };
+}
+
+/**
+ * Converts an internal add-on type to the type presented through the API.
+ *
+ * @param  aType
+ *         The internal add-on type
+ * @return an external add-on type
+ */
+function getExternalType(aType) {
+  if (aType in TYPE_ALIASES)
+    return TYPE_ALIASES[aType];
+  return aType;
+}
+
+function getManifestFileForDir(aDir) {
+  let file = aDir.clone();
+  file.append(FILE_RDF_MANIFEST);
+  if (file.exists() && file.isFile())
+    return file;
+  file.leafName = FILE_WEB_MANIFEST;
+  if (file.exists() && file.isFile())
+    return file;
+  return null;
+}
+
+function getManifestEntryForZipReader(aZipReader) {
+  if (aZipReader.hasEntry(FILE_RDF_MANIFEST))
+    return FILE_RDF_MANIFEST;
+  if (aZipReader.hasEntry(FILE_WEB_MANIFEST))
+    return FILE_WEB_MANIFEST;
+  return null;
+}
+
+/**
+ * Converts a list of API types to a list of API types and any aliases for those
+ * types.
+ *
+ * @param  aTypes
+ *         An array of types or null for all types
+ * @return an array of types or null for all types
+ */
+function getAllAliasesForTypes(aTypes) {
+  if (!aTypes)
+    return null;
+
+  // Build a set of all requested types and their aliases
+  let typeset = new Set(aTypes);
+
+  for (let alias of Object.keys(TYPE_ALIASES)) {
+    // Ignore any requested internal types
+    typeset.delete(alias);
+
+    // Add any alias for the internal type
+    if (typeset.has(TYPE_ALIASES[alias]))
+      typeset.add(alias);
+  }
+
+  return [...typeset];
+}
+
+/**
+ * Converts an RDF literal, resource or integer into a string.
+ *
+ * @param  aLiteral
+ *         The RDF object to convert
+ * @return a string if the object could be converted or null
+ */
+function getRDFValue(aLiteral) {
+  if (aLiteral instanceof Ci.nsIRDFLiteral)
+    return aLiteral.Value;
+  if (aLiteral instanceof Ci.nsIRDFResource)
+    return aLiteral.Value;
+  if (aLiteral instanceof Ci.nsIRDFInt)
+    return aLiteral.Value;
+  return null;
+}
+
+/**
+ * Gets an RDF property as a string
+ *
+ * @param  aDs
+ *         The RDF datasource to read the property from
+ * @param  aResource
+ *         The RDF resource to read the property from
+ * @param  aProperty
+ *         The property to read
+ * @return a string if the property existed or null
+ */
+function getRDFProperty(aDs, aResource, aProperty) {
+  return getRDFValue(aDs.GetTarget(aResource, EM_R(aProperty), true));
+}
+
+/**
+ * Reads an AddonInternal object from a manifest stream.
+ *
+ * @param  aUri
+ *         A |file:| or |jar:| URL for the manifest
+ * @return an AddonInternal object
+ * @throws if the install manifest in the stream is corrupt or could not
+ *         be read
+ */
+var loadManifestFromWebManifest = Task.async(function*(aUri) {
+  // We're passed the URI for the manifest file. Get the URI for its
+  // parent directory.
+  let uri = NetUtil.newURI("./", null, aUri);
+
+  let extension = new ExtensionData(uri);
+
+  let manifest = yield extension.readManifest();
+
+  // Read the list of available locales, and pre-load messages for
+  // all locales.
+  let locales = yield extension.initAllLocales();
+
+  // If there were any errors loading the extension, bail out now.
+  if (extension.errors.length)
+    throw new Error("Extension is invalid");
+
+  let bss = (manifest.browser_specific_settings && manifest.browser_specific_settings.gecko)
+      || (manifest.applications && manifest.applications.gecko) || {};
+  if (manifest.browser_specific_settings && manifest.applications) {
+    logger.warn("Ignoring applications property in manifest");
+  }
+
+  // A * is illegal in strict_min_version
+  if (bss.strict_min_version && bss.strict_min_version.split(".").some(part => part == "*")) {
+    throw new Error("The use of '*' in strict_min_version is invalid");
+  }
+
+  let addon = new AddonInternal();
+  addon.id = bss.id;
+  addon.version = manifest.version;
+  addon.type = "webextension";
+  addon.unpack = false;
+  addon.strictCompatibility = true;
+  addon.bootstrap = true;
+  addon.hasBinaryComponents = false;
+  addon.multiprocessCompatible = true;
+  addon.internalName = null;
+  addon.updateURL = bss.update_url;
+  addon.updateKey = null;
+  addon.optionsURL = null;
+  addon.optionsType = null;
+  addon.aboutURL = null;
+  addon.dependencies = Object.freeze(Array.from(extension.dependencies));
+
+  if (manifest.options_ui) {
+    // Store just the relative path here, the AddonWrapper getURL
+    // wrapper maps this to a full URL.
+    addon.optionsURL = manifest.options_ui.page;
+    if (manifest.options_ui.open_in_tab)
+      addon.optionsType = AddonManager.OPTIONS_TYPE_TAB;
+    else
+      addon.optionsType = AddonManager.OPTIONS_TYPE_INLINE_BROWSER;
+  }
+
+  // WebExtensions don't use iconURLs
+  addon.iconURL = null;
+  addon.icon64URL = null;
+  addon.icons = manifest.icons || {};
+
+  addon.applyBackgroundUpdates = AddonManager.AUTOUPDATE_DEFAULT;
+
+  function getLocale(aLocale) {
+    // Use the raw manifest, here, since we need values with their
+    // localization placeholders still in place.
+    let rawManifest = extension.rawManifest;
+
+    // As a convenience, allow author to be set if its a string bug 1313567.
+    let creator = typeof(rawManifest.author) === 'string' ? rawManifest.author : null;
+    let homepageURL = rawManifest.homepage_url;
+
+    // Allow developer to override creator and homepage_url.
+    if (rawManifest.developer) {
+      if (rawManifest.developer.name) {
+        creator = rawManifest.developer.name;
+      }
+      if (rawManifest.developer.url) {
+        homepageURL = rawManifest.developer.url;
+      }
+    }
+
+    let result = {
+      name: extension.localize(rawManifest.name, aLocale),
+      description: extension.localize(rawManifest.description, aLocale),
+      creator: extension.localize(creator, aLocale),
+      homepageURL: extension.localize(homepageURL, aLocale),
+
+      developers: null,
+      translators: null,
+      contributors: null,
+      locales: [aLocale],
+    };
+    return result;
+  }
+
+  addon.defaultLocale = getLocale(extension.defaultLocale);
+  addon.locales = Array.from(locales.keys(), getLocale);
+
+  delete addon.defaultLocale.locales;
+
+  addon.targetApplications = [{
+    id: TOOLKIT_ID,
+    minVersion: bss.strict_min_version,
+    maxVersion: bss.strict_max_version,
+  }];
+
+  addon.targetPlatforms = [];
+  addon.userDisabled = false;
+  addon.softDisabled = addon.blocklistState == Blocklist.STATE_SOFTBLOCKED;
+
+  return addon;
+});
+
+/**
+ * Reads an AddonInternal object from an RDF stream.
+ *
+ * @param  aUri
+ *         The URI that the manifest is being read from
+ * @param  aStream
+ *         An open stream to read the RDF from
+ * @return an AddonInternal object
+ * @throws if the install manifest in the RDF stream is corrupt or could not
+ *         be read
+ */
+let loadManifestFromRDF = Task.async(function*(aUri, aStream) {
+  function getPropertyArray(aDs, aSource, aProperty) {
+    let values = [];
+    let targets = aDs.GetTargets(aSource, EM_R(aProperty), true);
+    while (targets.hasMoreElements())
+      values.push(getRDFValue(targets.getNext()));
+
+    return values;
+  }
+
+  /**
+   * Reads locale properties from either the main install manifest root or
+   * an em:localized section in the install manifest.
+   *
+   * @param  aDs
+   *         The nsIRDFDatasource to read from
+   * @param  aSource
+   *         The nsIRDFResource to read the properties from
+   * @param  isDefault
+   *         True if the locale is to be read from the main install manifest
+   *         root
+   * @param  aSeenLocales
+   *         An array of locale names already seen for this install manifest.
+   *         Any locale names seen as a part of this function will be added to
+   *         this array
+   * @return an object containing the locale properties
+   */
+  function readLocale(aDs, aSource, isDefault, aSeenLocales) {
+    let locale = { };
+    if (!isDefault) {
+      locale.locales = [];
+      let targets = ds.GetTargets(aSource, EM_R("locale"), true);
+      while (targets.hasMoreElements()) {
+        let localeName = getRDFValue(targets.getNext());
+        if (!localeName) {
+          logger.warn("Ignoring empty locale in localized properties");
+          continue;
+        }
+        if (aSeenLocales.indexOf(localeName) != -1) {
+          logger.warn("Ignoring duplicate locale in localized properties");
+          continue;
+        }
+        aSeenLocales.push(localeName);
+        locale.locales.push(localeName);
+      }
+
+      if (locale.locales.length == 0) {
+        logger.warn("Ignoring localized properties with no listed locales");
+        return null;
+      }
+    }
+
+    for (let prop of PROP_LOCALE_SINGLE) {
+      locale[prop] = getRDFProperty(aDs, aSource, prop);
+    }
+
+    for (let prop of PROP_LOCALE_MULTI) {
+      // Don't store empty arrays
+      let props = getPropertyArray(aDs, aSource,
+                                   prop.substring(0, prop.length - 1));
+      if (props.length > 0)
+        locale[prop] = props;
+    }
+
+    return locale;
+  }
+
+  let rdfParser = Cc["@mozilla.org/rdf/xml-parser;1"].
+                  createInstance(Ci.nsIRDFXMLParser)
+  let ds = Cc["@mozilla.org/rdf/datasource;1?name=in-memory-datasource"].
+           createInstance(Ci.nsIRDFDataSource);
+  let listener = rdfParser.parseAsync(ds, aUri);
+  let channel = Cc["@mozilla.org/network/input-stream-channel;1"].
+                createInstance(Ci.nsIInputStreamChannel);
+  channel.setURI(aUri);
+  channel.contentStream = aStream;
+  channel.QueryInterface(Ci.nsIChannel);
+  channel.contentType = "text/xml";
+
+  listener.onStartRequest(channel, null);
+
+  try {
+    let pos = 0;
+    let count = aStream.available();
+    while (count > 0) {
+      listener.onDataAvailable(channel, null, aStream, pos, count);
+      pos += count;
+      count = aStream.available();
+    }
+    listener.onStopRequest(channel, null, Components.results.NS_OK);
+  }
+  catch (e) {
+    listener.onStopRequest(channel, null, e.result);
+    throw e;
+  }
+
+  let root = gRDF.GetResource(RDFURI_INSTALL_MANIFEST_ROOT);
+  let addon = new AddonInternal();
+  for (let prop of PROP_METADATA) {
+    addon[prop] = getRDFProperty(ds, root, prop);
+  }
+  addon.unpack = getRDFProperty(ds, root, "unpack") == "true";
+
+  if (!addon.type) {
+    addon.type = addon.internalName ? "theme" : "extension";
+  }
+  else {
+    let type = addon.type;
+    addon.type = null;
+    for (let name in TYPES) {
+      if (TYPES[name] == type) {
+        addon.type = name;
+        break;
+      }
+    }
+  }
+
+  if (!(addon.type in TYPES))
+    throw new Error("Install manifest specifies unknown type: " + addon.type);
+
+  if (addon.type != "multipackage") {
+    if (!addon.id)
+      throw new Error("No ID in install manifest");
+    if (!gIDTest.test(addon.id))
+      throw new Error("Illegal add-on ID " + addon.id);
+    if (!addon.version)
+      throw new Error("No version in install manifest");
+  }
+
+  addon.strictCompatibility = !(addon.type in COMPATIBLE_BY_DEFAULT_TYPES) ||
+                              getRDFProperty(ds, root, "strictCompatibility") == "true";
+
+  // Only read these properties for extensions.
+  if (addon.type == "extension") {
+    addon.bootstrap = getRDFProperty(ds, root, "bootstrap") == "true";
+
+    let mpcValue = getRDFProperty(ds, root, "multiprocessCompatible");
+    addon.multiprocessCompatible = mpcValue == "true";
+    addon.mpcOptedOut = mpcValue == "false";
+
+    addon.hasEmbeddedWebExtension = getRDFProperty(ds, root, "hasEmbeddedWebExtension") == "true";
+
+    if (addon.optionsType &&
+        addon.optionsType != AddonManager.OPTIONS_TYPE_DIALOG &&
+        addon.optionsType != AddonManager.OPTIONS_TYPE_INLINE &&
+        addon.optionsType != AddonManager.OPTIONS_TYPE_TAB &&
+        addon.optionsType != AddonManager.OPTIONS_TYPE_INLINE_INFO) {
+      throw new Error("Install manifest specifies unknown type: " + addon.optionsType);
+    }
+
+    if (addon.hasEmbeddedWebExtension) {
+      let uri = NetUtil.newURI("webextension/manifest.json", null, aUri);
+      let embeddedAddon = yield loadManifestFromWebManifest(uri);
+      if (embeddedAddon.optionsURL) {
+        if (addon.optionsType || addon.optionsURL)
+          logger.warn(`Addon ${addon.id} specifies optionsType or optionsURL ` +
+                      `in both install.rdf and manifest.json`);
+
+        addon.optionsURL = embeddedAddon.optionsURL;
+        addon.optionsType = embeddedAddon.optionsType;
+      }
+    }
+  }
+  else {
+    // Some add-on types are always restartless.
+    if (RESTARTLESS_TYPES.has(addon.type)) {
+      addon.bootstrap = true;
+    }
+
+    // Only extensions are allowed to provide an optionsURL, optionsType or aboutURL. For
+    // all other types they are silently ignored
+    addon.optionsURL = null;
+    addon.optionsType = null;
+    addon.aboutURL = null;
+
+    if (addon.type == "theme") {
+      if (!addon.internalName)
+        throw new Error("Themes must include an internalName property");
+      addon.skinnable = getRDFProperty(ds, root, "skinnable") == "true";
+    }
+  }
+
+  addon.defaultLocale = readLocale(ds, root, true);
+
+  let seenLocales = [];
+  addon.locales = [];
+  let targets = ds.GetTargets(root, EM_R("localized"), true);
+  while (targets.hasMoreElements()) {
+    let target = targets.getNext().QueryInterface(Ci.nsIRDFResource);
+    let locale = readLocale(ds, target, false, seenLocales);
+    if (locale)
+      addon.locales.push(locale);
+  }
+
+  let dependencies = new Set();
+  targets = ds.GetTargets(root, EM_R("dependency"), true);
+  while (targets.hasMoreElements()) {
+    let target = targets.getNext().QueryInterface(Ci.nsIRDFResource);
+    let id = getRDFProperty(ds, target, "id");
+    dependencies.add(id);
+  }
+  addon.dependencies = Object.freeze(Array.from(dependencies));
+
+  let seenApplications = [];
+  addon.targetApplications = [];
+  targets = ds.GetTargets(root, EM_R("targetApplication"), true);
+  while (targets.hasMoreElements()) {
+    let target = targets.getNext().QueryInterface(Ci.nsIRDFResource);
+    let targetAppInfo = {};
+    for (let prop of PROP_TARGETAPP) {
+      targetAppInfo[prop] = getRDFProperty(ds, target, prop);
+    }
+    if (!targetAppInfo.id || !targetAppInfo.minVersion ||
+        !targetAppInfo.maxVersion) {
+      logger.warn("Ignoring invalid targetApplication entry in install manifest");
+      continue;
+    }
+    if (seenApplications.indexOf(targetAppInfo.id) != -1) {
+      logger.warn("Ignoring duplicate targetApplication entry for " + targetAppInfo.id +
+           " in install manifest");
+      continue;
+    }
+    seenApplications.push(targetAppInfo.id);
+    addon.targetApplications.push(targetAppInfo);
+  }
+
+  // Note that we don't need to check for duplicate targetPlatform entries since
+  // the RDF service coalesces them for us.
+  let targetPlatforms = getPropertyArray(ds, root, "targetPlatform");
+  addon.targetPlatforms = [];
+  for (let targetPlatform of targetPlatforms) {
+    let platform = {
+      os: null,
+      abi: null
+    };
+
+    let pos = targetPlatform.indexOf("_");
+    if (pos != -1) {
+      platform.os = targetPlatform.substring(0, pos);
+      platform.abi = targetPlatform.substring(pos + 1);
+    }
+    else {
+      platform.os = targetPlatform;
+    }
+
+    addon.targetPlatforms.push(platform);
+  }
+
+  // A theme's userDisabled value is true if the theme is not the selected skin
+  // or if there is an active lightweight theme. We ignore whether softblocking
+  // is in effect since it would change the active theme.
+  if (addon.type == "theme") {
+    addon.userDisabled = !!LightweightThemeManager.currentTheme ||
+                         addon.internalName != XPIProvider.selectedSkin;
+  }
+  else if (addon.type == "experiment") {
+    // Experiments are disabled by default. It is up to the Experiments Manager
+    // to enable them (it drives installation).
+    addon.userDisabled = true;
+  }
+  else {
+    addon.userDisabled = false;
+  }
+
+  addon.softDisabled = addon.blocklistState == Blocklist.STATE_SOFTBLOCKED;
+  addon.applyBackgroundUpdates = AddonManager.AUTOUPDATE_DEFAULT;
+
+  // Experiments are managed and updated through an external "experiments
+  // manager." So disable some built-in mechanisms.
+  if (addon.type == "experiment") {
+    addon.applyBackgroundUpdates = AddonManager.AUTOUPDATE_DISABLE;
+    addon.updateURL = null;
+    addon.updateKey = null;
+  }
+
+  // icons will be filled by the calling function
+  addon.icons = {};
+
+  return addon;
+});
+
+function defineSyncGUID(aAddon) {
+  // Define .syncGUID as a lazy property which is also settable
+  Object.defineProperty(aAddon, "syncGUID", {
+    get: () => {
+      // Generate random GUID used for Sync.
+      let guid = Cc["@mozilla.org/uuid-generator;1"]
+          .getService(Ci.nsIUUIDGenerator)
+          .generateUUID().toString();
+
+      delete aAddon.syncGUID;
+      aAddon.syncGUID = guid;
+      return guid;
+    },
+    set: (val) => {
+      delete aAddon.syncGUID;
+      aAddon.syncGUID = val;
+    },
+    configurable: true,
+    enumerable: true,
+  });
+}
+
+// Generate a unique ID based on the path to this temporary add-on location.
+function generateTemporaryInstallID(aFile) {
+  const hasher = Cc["@mozilla.org/security/hash;1"]
+        .createInstance(Ci.nsICryptoHash);
+  hasher.init(hasher.SHA1);
+  const data = new TextEncoder().encode(aFile.path);
+  // Make it so this ID cannot be guessed.
+  const sess = TEMP_INSTALL_ID_GEN_SESSION;
+  hasher.update(sess, sess.length);
+  hasher.update(data, data.length);
+  let id = `${getHashStringForCrypto(hasher)}@temporary-addon`;
+  logger.info(`Generated temp id ${id} (${sess.join("")}) for ${aFile.path}`);
+  return id;
+}
+
+/**
+ * Loads an AddonInternal object from an add-on extracted in a directory.
+ *
+ * @param  aDir
+ *         The nsIFile directory holding the add-on
+ * @return an AddonInternal object
+ * @throws if the directory does not contain a valid install manifest
+ */
+var loadManifestFromDir = Task.async(function*(aDir, aInstallLocation) {
+  function getFileSize(aFile) {
+    if (aFile.isSymlink())
+      return 0;
+
+    if (!aFile.isDirectory())
+      return aFile.fileSize;
+
+    let size = 0;
+    let entries = aFile.directoryEntries.QueryInterface(Ci.nsIDirectoryEnumerator);
+    let entry;
+    while ((entry = entries.nextFile))
+      size += getFileSize(entry);
+    entries.close();
+    return size;
+  }
+
+  function* loadFromRDF(aUri) {
+    let fis = Cc["@mozilla.org/network/file-input-stream;1"].
+              createInstance(Ci.nsIFileInputStream);
+    fis.init(aUri.file, -1, -1, false);
+    let bis = Cc["@mozilla.org/network/buffered-input-stream;1"].
+              createInstance(Ci.nsIBufferedInputStream);
+    bis.init(fis, 4096);
+    try {
+      var addon = yield loadManifestFromRDF(aUri, bis);
+    } finally {
+      bis.close();
+      fis.close();
+    }
+
+    let iconFile = aDir.clone();
+    iconFile.append("icon.png");
+
+    if (iconFile.exists()) {
+      addon.icons[32] = "icon.png";
+      addon.icons[48] = "icon.png";
+    }
+
+    let icon64File = aDir.clone();
+    icon64File.append("icon64.png");
+
+    if (icon64File.exists()) {
+      addon.icons[64] = "icon64.png";
+    }
+
+    let file = aDir.clone();
+    file.append("chrome.manifest");
+    let chromeManifest = ChromeManifestParser.parseSync(Services.io.newFileURI(file));
+    addon.hasBinaryComponents = ChromeManifestParser.hasType(chromeManifest,
+                                                             "binary-component");
+    return addon;
+  }
+
+  let file = getManifestFileForDir(aDir);
+  if (!file) {
+    throw new Error("Directory " + aDir.path + " does not contain a valid " +
+                    "install manifest");
+  }
+
+  let uri = Services.io.newFileURI(file).QueryInterface(Ci.nsIFileURL);
+
+  let addon;
+  if (file.leafName == FILE_WEB_MANIFEST) {
+    addon = yield loadManifestFromWebManifest(uri);
+    if (!addon.id) {
+      if (aInstallLocation == TemporaryInstallLocation) {
+        addon.id = generateTemporaryInstallID(aDir);
+      } else {
+        addon.id = aDir.leafName;
+      }
+    }
+  } else {
+    addon = yield loadFromRDF(uri);
+  }
+
+  addon._sourceBundle = aDir.clone();
+  addon._installLocation = aInstallLocation;
+  addon.size = getFileSize(aDir);
+  addon.signedState = yield verifyDirSignedState(aDir, addon)
+    .then(({signedState}) => signedState);
+  addon.appDisabled = !isUsableAddon(addon);
+
+  defineSyncGUID(addon);
+
+  return addon;
+});
+
+/**
+ * Loads an AddonInternal object from an nsIZipReader for an add-on.
+ *
+ * @param  aZipReader
+ *         An open nsIZipReader for the add-on's files
+ * @return an AddonInternal object
+ * @throws if the XPI file does not contain a valid install manifest
+ */
+var loadManifestFromZipReader = Task.async(function*(aZipReader, aInstallLocation) {
+  function* loadFromRDF(aUri) {
+    let zis = aZipReader.getInputStream(entry);
+    let bis = Cc["@mozilla.org/network/buffered-input-stream;1"].
+              createInstance(Ci.nsIBufferedInputStream);
+    bis.init(zis, 4096);
+    try {
+      var addon = yield loadManifestFromRDF(aUri, bis);
+    } finally {
+      bis.close();
+      zis.close();
+    }
+
+    if (aZipReader.hasEntry("icon.png")) {
+      addon.icons[32] = "icon.png";
+      addon.icons[48] = "icon.png";
+    }
+
+    if (aZipReader.hasEntry("icon64.png")) {
+      addon.icons[64] = "icon64.png";
+    }
+
+    // Binary components can only be loaded from unpacked addons.
+    if (addon.unpack) {
+      let uri = buildJarURI(aZipReader.file, "chrome.manifest");
+      let chromeManifest = ChromeManifestParser.parseSync(uri);
+      addon.hasBinaryComponents = ChromeManifestParser.hasType(chromeManifest,
+                                                               "binary-component");
+    } else {
+      addon.hasBinaryComponents = false;
+    }
+
+    return addon;
+  }
+
+  let entry = getManifestEntryForZipReader(aZipReader);
+  if (!entry) {
+    throw new Error("File " + aZipReader.file.path + " does not contain a valid " +
+                    "install manifest");
+  }
+
+  let uri = buildJarURI(aZipReader.file, entry);
+
+  let isWebExtension = (entry == FILE_WEB_MANIFEST);
+
+  let addon = isWebExtension ?
+              yield loadManifestFromWebManifest(uri) :
+              yield loadFromRDF(uri);
+
+  addon._sourceBundle = aZipReader.file;
+  addon._installLocation = aInstallLocation;
+
+  addon.size = 0;
+  let entries = aZipReader.findEntries(null);
+  while (entries.hasMore())
+    addon.size += aZipReader.getEntry(entries.getNext()).realSize;
+
+  let {signedState, cert} = yield verifyZipSignedState(aZipReader.file, addon);
+  addon.signedState = signedState;
+  if (isWebExtension && !addon.id) {
+    if (cert) {
+      addon.id = cert.commonName;
+      if (!gIDTest.test(addon.id)) {
+        throw new Error(`Webextension is signed with an invalid id (${addon.id})`);
+      }
+    }
+    if (!addon.id && aInstallLocation == TemporaryInstallLocation) {
+      addon.id = generateTemporaryInstallID(aZipReader.file);
+    }
+  }
+  addon.appDisabled = !isUsableAddon(addon);
+
+  defineSyncGUID(addon);
+
+  return addon;
+});
+
+/**
+ * Loads an AddonInternal object from an add-on in an XPI file.
+ *
+ * @param  aXPIFile
+ *         An nsIFile pointing to the add-on's XPI file
+ * @return an AddonInternal object
+ * @throws if the XPI file does not contain a valid install manifest
+ */
+var loadManifestFromZipFile = Task.async(function*(aXPIFile, aInstallLocation) {
+  let zipReader = Cc["@mozilla.org/libjar/zip-reader;1"].
+                  createInstance(Ci.nsIZipReader);
+  try {
+    zipReader.open(aXPIFile);
+
+    // Can't return this promise because that will make us close the zip reader
+    // before it has finished loading the manifest. Wait for the result and then
+    // return.
+    let manifest = yield loadManifestFromZipReader(zipReader, aInstallLocation);
+    return manifest;
+  }
+  finally {
+    zipReader.close();
+  }
+});
+
+function loadManifestFromFile(aFile, aInstallLocation) {
+  if (aFile.isFile())
+    return loadManifestFromZipFile(aFile, aInstallLocation);
+  return loadManifestFromDir(aFile, aInstallLocation);
+}
+
+/**
+ * A synchronous method for loading an add-on's manifest. This should only ever
+ * be used during startup or a sync load of the add-ons DB
+ */
+function syncLoadManifestFromFile(aFile, aInstallLocation) {
+  let success = undefined;
+  let result = null;
+
+  loadManifestFromFile(aFile, aInstallLocation).then(val => {
+    success = true;
+    result = val;
+  }, val => {
+    success = false;
+    result = val
+  });
+
+  let thread = Services.tm.currentThread;
+
+  while (success === undefined)
+    thread.processNextEvent(true);
+
+  if (!success)
+    throw result;
+  return result;
+}
+
+/**
+ * Gets an nsIURI for a file within another file, either a directory or an XPI
+ * file. If aFile is a directory then this will return a file: URI, if it is an
+ * XPI file then it will return a jar: URI.
+ *
+ * @param  aFile
+ *         The file containing the resources, must be either a directory or an
+ *         XPI file
+ * @param  aPath
+ *         The path to find the resource at, "/" separated. If aPath is empty
+ *         then the uri to the root of the contained files will be returned
+ * @return an nsIURI pointing at the resource
+ */
+function getURIForResourceInFile(aFile, aPath) {
+  if (aFile.isDirectory()) {
+    let resource = aFile.clone();
+    if (aPath)
+      aPath.split("/").forEach(part => resource.append(part));
+
+    return NetUtil.newURI(resource);
+  }
+
+  return buildJarURI(aFile, aPath);
+}
+
+/**
+ * Creates a jar: URI for a file inside a ZIP file.
+ *
+ * @param  aJarfile
+ *         The ZIP file as an nsIFile
+ * @param  aPath
+ *         The path inside the ZIP file
+ * @return an nsIURI for the file
+ */
+function buildJarURI(aJarfile, aPath) {
+  let uri = Services.io.newFileURI(aJarfile);
+  uri = "jar:" + uri.spec + "!/" + aPath;
+  return NetUtil.newURI(uri);
+}
+
+/**
+ * Sends local and remote notifications to flush a JAR file cache entry
+ *
+ * @param aJarFile
+ *        The ZIP/XPI/JAR file as a nsIFile
+ */
+function flushJarCache(aJarFile) {
+  Services.obs.notifyObservers(aJarFile, "flush-cache-entry", null);
+  Services.mm.broadcastAsyncMessage(MSG_JAR_FLUSH, aJarFile.path);
+}
+
+function flushChromeCaches() {
+  // Init this, so it will get the notification.
+  Services.obs.notifyObservers(null, "startupcache-invalidate", null);
+  // Flush message manager cached scripts
+  Services.obs.notifyObservers(null, "message-manager-flush-caches", null);
+  // Also dispatch this event to child processes
+  Services.mm.broadcastAsyncMessage(MSG_MESSAGE_MANAGER_CACHES_FLUSH, null);
+}
+
+/**
+ * Creates and returns a new unique temporary file. The caller should delete
+ * the file when it is no longer needed.
+ *
+ * @return an nsIFile that points to a randomly named, initially empty file in
+ *         the OS temporary files directory
+ */
+function getTemporaryFile() {
+  let file = FileUtils.getDir(KEY_TEMPDIR, []);
+  let random = Math.random().toString(36).replace(/0./, '').substr(-3);
+  file.append("tmp-" + random + ".xpi");
+  file.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, FileUtils.PERMS_FILE);
+
+  return file;
+}
+
+/**
+ * Verifies that a zip file's contents are all signed by the same principal.
+ * Directory entries and anything in the META-INF directory are not checked.
+ *
+ * @param  aZip
+ *         A nsIZipReader to check
+ * @param  aCertificate
+ *         The nsIX509Cert to compare against
+ * @return true if all the contents that should be signed were signed by the
+ *         principal
+ */
+function verifyZipSigning(aZip, aCertificate) {
+  var count = 0;
+  var entries = aZip.findEntries(null);
+  while (entries.hasMore()) {
+    var entry = entries.getNext();
+    // Nothing in META-INF is in the manifest.
+    if (entry.substr(0, 9) == "META-INF/")
+      continue;
+    // Directory entries aren't in the manifest.
+    if (entry.substr(-1) == "/")
+      continue;
+    count++;
+    var entryCertificate = aZip.getSigningCert(entry);
+    if (!entryCertificate || !aCertificate.equals(entryCertificate)) {
+      return false;
+    }
+  }
+  return aZip.manifestEntriesCount == count;
+}
+
+/**
+ * Returns the signedState for a given return code and certificate by verifying
+ * it against the expected ID.
+ */
+function getSignedStatus(aRv, aCert, aAddonID) {
+  let expectedCommonName = aAddonID;
+  if (aAddonID && aAddonID.length > 64) {
+    let converter = Cc["@mozilla.org/intl/scriptableunicodeconverter"].
+                    createInstance(Ci.nsIScriptableUnicodeConverter);
+    converter.charset = "UTF-8";
+    let data = converter.convertToByteArray(aAddonID, {});
+
+    let crypto = Cc["@mozilla.org/security/hash;1"].
+                 createInstance(Ci.nsICryptoHash);
+    crypto.init(Ci.nsICryptoHash.SHA256);
+    crypto.update(data, data.length);
+    expectedCommonName = getHashStringForCrypto(crypto);
+  }
+
+  switch (aRv) {
+    case Cr.NS_OK:
+      if (expectedCommonName && expectedCommonName != aCert.commonName)
+        return AddonManager.SIGNEDSTATE_BROKEN;
+
+      let hotfixID = Preferences.get(PREF_EM_HOTFIX_ID, undefined);
+      if (hotfixID && hotfixID == aAddonID && Preferences.get(PREF_EM_CERT_CHECKATTRIBUTES, false)) {
+        // The hotfix add-on has some more rigorous certificate checks
+        try {
+          CertUtils.validateCert(aCert,
+                                 CertUtils.readCertPrefs(PREF_EM_HOTFIX_CERTS));
+        }
+        catch (e) {
+          logger.warn("The hotfix add-on was not signed by the expected " +
+                      "certificate and so will not be installed.", e);
+          return AddonManager.SIGNEDSTATE_BROKEN;
+        }
+      }
+
+      if (aCert.organizationalUnit == "Mozilla Components")
+        return AddonManager.SIGNEDSTATE_SYSTEM;
+
+      return /preliminary/i.test(aCert.organizationalUnit)
+               ? AddonManager.SIGNEDSTATE_PRELIMINARY
+               : AddonManager.SIGNEDSTATE_SIGNED;
+    case Cr.NS_ERROR_SIGNED_JAR_NOT_SIGNED:
+      return AddonManager.SIGNEDSTATE_MISSING;
+    case Cr.NS_ERROR_SIGNED_JAR_MANIFEST_INVALID:
+    case Cr.NS_ERROR_SIGNED_JAR_ENTRY_INVALID:
+    case Cr.NS_ERROR_SIGNED_JAR_ENTRY_MISSING:
+    case Cr.NS_ERROR_SIGNED_JAR_ENTRY_TOO_LARGE:
+    case Cr.NS_ERROR_SIGNED_JAR_UNSIGNED_ENTRY:
+    case Cr.NS_ERROR_SIGNED_JAR_MODIFIED_ENTRY:
+      return AddonManager.SIGNEDSTATE_BROKEN;
+    default:
+      // Any other error indicates that either the add-on isn't signed or it
+      // is signed by a signature that doesn't chain to the trusted root.
+      return AddonManager.SIGNEDSTATE_UNKNOWN;
+  }
+}
+
+function shouldVerifySignedState(aAddon) {
+  // Updated system add-ons should always have their signature checked
+  if (aAddon._installLocation.name == KEY_APP_SYSTEM_ADDONS)
+    return true;
+
+  // We don't care about signatures for default system add-ons
+  if (aAddon._installLocation.name == KEY_APP_SYSTEM_DEFAULTS)
+    return false;
+
+  // Hotfixes should always have their signature checked
+  let hotfixID = Preferences.get(PREF_EM_HOTFIX_ID, undefined);
+  if (hotfixID && aAddon.id == hotfixID)
+    return true;
+
+  // Otherwise only check signatures if signing is enabled and the add-on is one
+  // of the signed types.
+  return ADDON_SIGNING && SIGNED_TYPES.has(aAddon.type);
+}
+
+let gCertDB = Cc["@mozilla.org/security/x509certdb;1"]
+              .getService(Ci.nsIX509CertDB);
+
+/**
+ * Verifies that a zip file's contents are all correctly signed by an
+ * AMO-issued certificate
+ *
+ * @param  aFile
+ *         the xpi file to check
+ * @param  aAddon
+ *         the add-on object to verify
+ * @return a Promise that resolves to an object with properties:
+ *         signedState: an AddonManager.SIGNEDSTATE_* constant
+ *         cert: an nsIX509Cert
+ */
+function verifyZipSignedState(aFile, aAddon) {
+  if (!shouldVerifySignedState(aAddon))
+    return Promise.resolve({
+      signedState: AddonManager.SIGNEDSTATE_NOT_REQUIRED,
+      cert: null
+    });
+
+  let root = Ci.nsIX509CertDB.AddonsPublicRoot;
+  if (!REQUIRE_SIGNING && Preferences.get(PREF_XPI_SIGNATURES_DEV_ROOT, false))
+    root = Ci.nsIX509CertDB.AddonsStageRoot;
+
+  return new Promise(resolve => {
+    let callback = {
+      openSignedAppFileFinished: function(aRv, aZipReader, aCert) {
+        if (aZipReader)
+          aZipReader.close();
+        resolve({
+          signedState: getSignedStatus(aRv, aCert, aAddon.id),
+          cert: aCert
+        });
+      }
+    };
+    // This allows the certificate DB to get the raw JS callback object so the
+    // test code can pass through objects that XPConnect would reject.
+    callback.wrappedJSObject = callback;
+
+    gCertDB.openSignedAppFileAsync(root, aFile, callback);
+  });
+}
+
+/**
+ * Verifies that a directory's contents are all correctly signed by an
+ * AMO-issued certificate
+ *
+ * @param  aDir
+ *         the directory to check
+ * @param  aAddon
+ *         the add-on object to verify
+ * @return a Promise that resolves to an object with properties:
+ *         signedState: an AddonManager.SIGNEDSTATE_* constant
+ *         cert: an nsIX509Cert
+ */
+function verifyDirSignedState(aDir, aAddon) {
+  if (!shouldVerifySignedState(aAddon))
+    return Promise.resolve({
+      signedState: AddonManager.SIGNEDSTATE_NOT_REQUIRED,
+      cert: null,
+    });
+
+  let root = Ci.nsIX509CertDB.AddonsPublicRoot;
+  if (!REQUIRE_SIGNING && Preferences.get(PREF_XPI_SIGNATURES_DEV_ROOT, false))
+    root = Ci.nsIX509CertDB.AddonsStageRoot;
+
+  return new Promise(resolve => {
+    let callback = {
+      verifySignedDirectoryFinished: function(aRv, aCert) {
+        resolve({
+          signedState: getSignedStatus(aRv, aCert, aAddon.id),
+          cert: null,
+        });
+      }
+    };
+    // This allows the certificate DB to get the raw JS callback object so the
+    // test code can pass through objects that XPConnect would reject.
+    callback.wrappedJSObject = callback;
+
+    gCertDB.verifySignedDirectoryAsync(root, aDir, callback);
+  });
+}
+
+/**
+ * Verifies that a bundle's contents are all correctly signed by an
+ * AMO-issued certificate
+ *
+ * @param  aBundle
+ *         the nsIFile for the bundle to check, either a directory or zip file
+ * @param  aAddon
+ *         the add-on object to verify
+ * @return a Promise that resolves to an AddonManager.SIGNEDSTATE_* constant.
+ */
+function verifyBundleSignedState(aBundle, aAddon) {
+  let promise = aBundle.isFile() ? verifyZipSignedState(aBundle, aAddon)
+      : verifyDirSignedState(aBundle, aAddon);
+  return promise.then(({signedState}) => signedState);
+}
+
+/**
+ * Replaces %...% strings in an addon url (update and updateInfo) with
+ * appropriate values.
+ *
+ * @param  aAddon
+ *         The AddonInternal representing the add-on
+ * @param  aUri
+ *         The uri to escape
+ * @param  aUpdateType
+ *         An optional number representing the type of update, only applicable
+ *         when creating a url for retrieving an update manifest
+ * @param  aAppVersion
+ *         The optional application version to use for %APP_VERSION%
+ * @return the appropriately escaped uri.
+ */
+function escapeAddonURI(aAddon, aUri, aUpdateType, aAppVersion)
+{
+  let uri = AddonManager.escapeAddonURI(aAddon, aUri, aAppVersion);
+
+  // If there is an updateType then replace the UPDATE_TYPE string
+  if (aUpdateType)
+    uri = uri.replace(/%UPDATE_TYPE%/g, aUpdateType);
+
+  // If this add-on has compatibility information for either the current
+  // application or toolkit then replace the ITEM_MAXAPPVERSION with the
+  // maxVersion
+  let app = aAddon.matchingTargetApplication;
+  if (app)
+    var maxVersion = app.maxVersion;
+  else
+    maxVersion = "";
+  uri = uri.replace(/%ITEM_MAXAPPVERSION%/g, maxVersion);
+
+  let compatMode = "normal";
+  if (!AddonManager.checkCompatibility)
+    compatMode = "ignore";
+  else if (AddonManager.strictCompatibility)
+    compatMode = "strict";
+  uri = uri.replace(/%COMPATIBILITY_MODE%/g, compatMode);
+
+  return uri;
+}
+
+function removeAsync(aFile) {
+  return Task.spawn(function*() {
+    let info = null;
+    try {
+      info = yield OS.File.stat(aFile.path);
+      if (info.isDir)
+        yield OS.File.removeDir(aFile.path);
+      else
+        yield OS.File.remove(aFile.path);
+    }
+    catch (e) {
+      if (!(e instanceof OS.File.Error) || ! e.becauseNoSuchFile)
+        throw e;
+      // The file has already gone away
+      return;
+    }
+  });
+}
+
+/**
+ * Recursively removes a directory or file fixing permissions when necessary.
+ *
+ * @param  aFile
+ *         The nsIFile to remove
+ */
+function recursiveRemove(aFile) {
+  let isDir = null;
+
+  try {
+    isDir = aFile.isDirectory();
+  }
+  catch (e) {
+    // If the file has already gone away then don't worry about it, this can
+    // happen on OSX where the resource fork is automatically moved with the
+    // data fork for the file. See bug 733436.
+    if (e.result == Cr.NS_ERROR_FILE_TARGET_DOES_NOT_EXIST)
+      return;
+    if (e.result == Cr.NS_ERROR_FILE_NOT_FOUND)
+      return;
+
+    throw e;
+  }
+
+  setFilePermissions(aFile, isDir ? FileUtils.PERMS_DIRECTORY
+                                  : FileUtils.PERMS_FILE);
+
+  try {
+    aFile.remove(true);
+    return;
+  }
+  catch (e) {
+    if (!aFile.isDirectory() || aFile.isSymlink()) {
+      logger.error("Failed to remove file " + aFile.path, e);
+      throw e;
+    }
+  }
+
+  // Use a snapshot of the directory contents to avoid possible issues with
+  // iterating over a directory while removing files from it (the YAFFS2
+  // embedded filesystem has this issue, see bug 772238), and to remove
+  // normal files before their resource forks on OSX (see bug 733436).
+  let entries = getDirectoryEntries(aFile, true);
+  entries.forEach(recursiveRemove);
+
+  try {
+    aFile.remove(true);
+  }
+  catch (e) {
+    logger.error("Failed to remove empty directory " + aFile.path, e);
+    throw e;
+  }
+}
+
+/**
+ * Returns the timestamp and leaf file name of the most recently modified
+ * entry in a directory,
+ * or simply the file's own timestamp if it is not a directory.
+ * Also returns the total number of items (directories and files) visited in the scan
+ *
+ * @param  aFile
+ *         A non-null nsIFile object
+ * @return [File Name, Epoch time, items visited], as described above.
+ */
+function recursiveLastModifiedTime(aFile) {
+  try {
+    let modTime = aFile.lastModifiedTime;
+    let fileName = aFile.leafName;
+    if (aFile.isFile())
+      return [fileName, modTime, 1];
+
+    if (aFile.isDirectory()) {
+      let entries = aFile.directoryEntries.QueryInterface(Ci.nsIDirectoryEnumerator);
+      let entry;
+      let totalItems = 1;
+      while ((entry = entries.nextFile)) {
+        let [subName, subTime, items] = recursiveLastModifiedTime(entry);
+        totalItems += items;
+        if (subTime > modTime) {
+          modTime = subTime;
+          fileName = subName;
+        }
+      }
+      entries.close();
+      return [fileName, modTime, totalItems];
+    }
+  }
+  catch (e) {
+    logger.warn("Problem getting last modified time for " + aFile.path, e);
+  }
+
+  // If the file is something else, just ignore it.
+  return ["", 0, 0];
+}
+
+/**
+ * Gets a snapshot of directory entries.
+ *
+ * @param  aDir
+ *         Directory to look at
+ * @param  aSortEntries
+ *         True to sort entries by filename
+ * @return An array of nsIFile, or an empty array if aDir is not a readable directory
+ */
+function getDirectoryEntries(aDir, aSortEntries) {
+  let dirEnum;
+  try {
+    dirEnum = aDir.directoryEntries.QueryInterface(Ci.nsIDirectoryEnumerator);
+    let entries = [];
+    while (dirEnum.hasMoreElements())
+      entries.push(dirEnum.nextFile);
+
+    if (aSortEntries) {
+      entries.sort(function(a, b) {
+        return a.path > b.path ? -1 : 1;
+      });
+    }
+
+    return entries
+  }
+  catch (e) {
+    logger.warn("Can't iterate directory " + aDir.path, e);
+    return [];
+  }
+  finally {
+    if (dirEnum) {
+      dirEnum.close();
+    }
+  }
+}
+
+/**
+ * Record a bit of per-addon telemetry
+ * @param aAddon the addon to record
+ */
+function recordAddonTelemetry(aAddon) {
+  let locale = aAddon.defaultLocale;
+  if (locale) {
+    if (locale.name)
+      XPIProvider.setTelemetry(aAddon.id, "name", locale.name);
+    if (locale.creator)
+      XPIProvider.setTelemetry(aAddon.id, "creator", locale.creator);
+  }
+}
+
+/**
+ * The on-disk state of an individual XPI, created from an Object
+ * as stored in the 'extensions.xpiState' pref.
+ */
+function XPIState(saved) {
+  for (let [short, long] of XPIState.prototype.fields) {
+    if (short in saved) {
+      this[long] = saved[short];
+    }
+  }
+}
+
+XPIState.prototype = {
+  fields: [['d', 'descriptor'],
+           ['e', 'enabled'],
+           ['v', 'version'],
+           ['st', 'scanTime'],
+           ['mt', 'manifestTime']],
+  /**
+   * Return the last modified time, based on enabled/disabled
+   */
+  get mtime() {
+    if (!this.enabled && ('manifestTime' in this) && this.manifestTime > this.scanTime) {
+      return this.manifestTime;
+    }
+    return this.scanTime;
+  },
+
+  toJSON() {
+    let json = {};
+    for (let [short, long] of XPIState.prototype.fields) {
+      if (long in this) {
+        json[short] = this[long];
+      }
+    }
+    return json;
+  },
+
+  /**
+   * Update the last modified time for an add-on on disk.
+   * @param aFile: nsIFile path of the add-on.
+   * @param aId: The add-on ID.
+   * @return True if the time stamp has changed.
+   */
+  getModTime(aFile, aId) {
+    let changed = false;
+    let scanStarted = Cu.now();
+    // For an unknown or enabled add-on, we do a full recursive scan.
+    if (!('scanTime' in this) || this.enabled) {
+      logger.debug('getModTime: Recursive scan of ' + aId);
+      let [modFile, modTime, items] = recursiveLastModifiedTime(aFile);
+      XPIProvider._mostRecentlyModifiedFile[aId] = modFile;
+      XPIProvider.setTelemetry(aId, "scan_items", items);
+      if (modTime != this.scanTime) {
+        this.scanTime = modTime;
+        changed = true;
+      }
+    }
+    // if the add-on is disabled, modified time is the install manifest time, if
+    // any. If no manifest exists, we assume this is a packed .xpi and use
+    // the time stamp of {path}
+    try {
+      // Get the install manifest update time, if any.
+      let maniFile = getManifestFileForDir(aFile);
+      if (!(aId in XPIProvider._mostRecentlyModifiedFile)) {
+        XPIProvider._mostRecentlyModifiedFile[aId] = maniFile.leafName;
+      }
+      let maniTime = maniFile.lastModifiedTime;
+      if (maniTime != this.manifestTime) {
+        this.manifestTime = maniTime;
+        changed = true;
+      }
+    } catch (e) {
+      // No manifest
+      delete this.manifestTime;
+      try {
+        let dtime = aFile.lastModifiedTime;
+        if (dtime != this.scanTime) {
+          changed = true;
+          this.scanTime = dtime;
+        }
+      } catch (e) {
+        logger.warn("Can't get modified time of ${file}: ${e}", {file: aFile.path, e: e});
+        changed = true;
+        this.scanTime = 0;
+      }
+    }
+    // Record duration of file-modified check
+    XPIProvider.setTelemetry(aId, "scan_MS", Math.round(Cu.now() - scanStarted));
+
+    return changed;
+  },
+
+  /**
+   * Update the XPIState to match an XPIDatabase entry; if 'enabled' is changed to true,
+   * update the last-modified time. This should probably be made async, but for now we
+   * don't want to maintain parallel sync and async versions of the scan.
+   * Caller is responsible for doing XPIStates.save() if necessary.
+   * @param aDBAddon The DBAddonInternal for this add-on.
+   * @param aUpdated The add-on was updated, so we must record new modified time.
+   */
+  syncWithDB(aDBAddon, aUpdated = false) {
+    logger.debug("Updating XPIState for " + JSON.stringify(aDBAddon));
+    // If the add-on changes from disabled to enabled, we should re-check the modified time.
+    // If this is a newly found add-on, it won't have an 'enabled' field but we
+    // did a full recursive scan in that case, so we don't need to do it again.
+    // We don't use aDBAddon.active here because it's not updated until after restart.
+    let mustGetMod = (aDBAddon.visible && !aDBAddon.disabled && !this.enabled);
+    this.enabled = (aDBAddon.visible && !aDBAddon.disabled);
+    this.version = aDBAddon.version;
+    // XXX Eventually also copy bootstrap, etc.
+    if (aUpdated || mustGetMod) {
+      this.getModTime(new nsIFile(this.descriptor), aDBAddon.id);
+      if (this.scanTime != aDBAddon.updateDate) {
+        aDBAddon.updateDate = this.scanTime;
+        XPIDatabase.saveChanges();
+      }
+    }
+  },
+};
+
+// Constructor for an ES6 Map that knows how to convert itself into a
+// regular object for toJSON().
+function SerializableMap() {
+  let m = new Map();
+  m.toJSON = function() {
+    let out = {}
+    for (let [key, val] of m) {
+      out[key] = val;
+    }
+    return out;
+  };
+  return m;
+}
+
+/**
+ * Keeps track of the state of XPI add-ons on the file system.
+ */
+this.XPIStates = {
+  // Map(location name -> Map(add-on ID -> XPIState))
+  db: null,
+
+  get size() {
+    if (!this.db) {
+      return 0;
+    }
+    let count = 0;
+    for (let location of this.db.values()) {
+      count += location.size;
+    }
+    return count;
+  },
+
+  /**
+   * Load extension state data from preferences.
+   */
+  loadExtensionState() {
+    let state = {};
+
+    // Clear out old directory state cache.
+    Preferences.reset(PREF_INSTALL_CACHE);
+
+    let cache = Preferences.get(PREF_XPI_STATE, "{}");
+    try {
+      state = JSON.parse(cache);
+    } catch (e) {
+      logger.warn("Error parsing extensions.xpiState ${state}: ${error}",
+          {state: cache, error: e});
+    }
+    logger.debug("Loaded add-on state from prefs: ${}", state);
+    return state;
+  },
+
+  /**
+   * Walk through all install locations, highest priority first,
+   * comparing the on-disk state of extensions to what is stored in prefs.
+   * @return true if anything has changed.
+   */
+  getInstallState() {
+    let oldState = this.loadExtensionState();
+    let changed = false;
+    this.db = new SerializableMap();
+
+    for (let location of XPIProvider.installLocations) {
+      // The list of add-on like file/directory names in the install location.
+      let addons = location.getAddonLocations();
+      // The results of scanning this location.
+      let foundAddons = new SerializableMap();
+
+      // What our old state thinks should be in this location.
+      let locState = {};
+      if (location.name in oldState) {
+        locState = oldState[location.name];
+        // We've seen this location.
+        delete oldState[location.name];
+      }
+
+      for (let [id, file] of addons) {
+        if (!(id in locState)) {
+          logger.debug("New add-on ${id} in ${location}", {id: id, location: location.name});
+          let xpiState = new XPIState({d: file.persistentDescriptor});
+          changed = xpiState.getModTime(file, id) || changed;
+          foundAddons.set(id, xpiState);
+        } else {
+          let xpiState = new XPIState(locState[id]);
+          // We found this add-on in the file system
+          delete locState[id];
+
+          changed = xpiState.getModTime(file, id) || changed;
+
+          if (file.persistentDescriptor != xpiState.descriptor) {
+            xpiState.descriptor = file.persistentDescriptor;
+            changed = true;
+          }
+          if (changed) {
+            logger.debug("Changed add-on ${id} in ${location}", {id: id, location: location.name});
+          }
+          else {
+            logger.debug("Existing add-on ${id} in ${location}", {id: id, location: location.name});
+          }
+          foundAddons.set(id, xpiState);
+        }
+        XPIProvider.setTelemetry(id, "location", location.name);
+      }
+
+      // Anything left behind in oldState was removed from the file system.
+      for (let id in locState) {
+        changed = true;
+        break;
+      }
+      // If we found anything, add this location to our database.
+      if (foundAddons.size != 0) {
+        this.db.set(location.name, foundAddons);
+      }
+    }
+
+    // If there's anything left in oldState, an install location that held add-ons
+    // was removed from the browser configuration.
+    for (let location in oldState) {
+      changed = true;
+      break;
+    }
+
+    logger.debug("getInstallState changed: ${rv}, state: ${state}",
+        {rv: changed, state: this.db});
+    return changed;
+  },
+
+  /**
+   * Get the Map of XPI states for a particular location.
+   * @param aLocation The name of the install location.
+   * @return Map (id -> XPIState) or null if there are no add-ons in the location.
+   */
+  getLocation(aLocation) {
+    return this.db.get(aLocation);
+  },
+
+  /**
+   * Get the XPI state for a specific add-on in a location.
+   * If the state is not in our cache, return null.
+   * @param aLocation The name of the location where the add-on is installed.
+   * @param aId       The add-on ID
+   * @return The XPIState entry for the add-on, or null.
+   */
+  getAddon(aLocation, aId) {
+    let location = this.db.get(aLocation);
+    if (!location) {
+      return null;
+    }
+    return location.get(aId);
+  },
+
+  /**
+   * Find the highest priority location of an add-on by ID and return the
+   * location and the XPIState.
+   * @param aId   The add-on ID
+   * @return [locationName, XPIState] if the add-on is found, [undefined, undefined]
+   *         if the add-on is not found.
+   */
+  findAddon(aId) {
+    // Fortunately the Map iterator returns in order of insertion, which is
+    // also our highest -> lowest priority order.
+    for (let [name, location] of this.db) {
+      if (location.has(aId)) {
+        return [name, location.get(aId)];
+      }
+    }
+    return [undefined, undefined];
+  },
+
+  /**
+   * Add a new XPIState for an add-on and synchronize it with the DBAddonInternal.
+   * @param aAddon DBAddonInternal for the new add-on.
+   */
+  addAddon(aAddon) {
+    let location = this.db.get(aAddon.location);
+    if (!location) {
+      // First add-on in this location.
+      location = new SerializableMap();
+      this.db.set(aAddon.location, location);
+    }
+    logger.debug("XPIStates adding add-on ${id} in ${location}: ${descriptor}", aAddon);
+    let xpiState = new XPIState({d: aAddon.descriptor});
+    location.set(aAddon.id, xpiState);
+    xpiState.syncWithDB(aAddon, true);
+    XPIProvider.setTelemetry(aAddon.id, "location", aAddon.location);
+  },
+
+  /**
+   * Save the current state of installed add-ons.
+   * XXX this *totally* should be a .json file using DeferredSave...
+   */
+  save() {
+    let cache = JSON.stringify(this.db);
+    Services.prefs.setCharPref(PREF_XPI_STATE, cache);
+  },
+
+  /**
+   * Remove the XPIState for an add-on and save the new state.
+   * @param aLocation  The name of the add-on location.
+   * @param aId        The ID of the add-on.
+   */
+  removeAddon(aLocation, aId) {
+    logger.debug("Removing XPIState for " + aLocation + ":" + aId);
+    let location = this.db.get(aLocation);
+    if (!location) {
+      return;
+    }
+    location.delete(aId);
+    if (location.size == 0) {
+      this.db.delete(aLocation);
+    }
+    this.save();
+  },
+};
+
+this.XPIProvider = {
+  get name() {
+    return "XPIProvider";
+  },
+
+  // An array of known install locations
+  installLocations: null,
+  // A dictionary of known install locations by name
+  installLocationsByName: null,
+  // An array of currently active AddonInstalls
+  installs: null,
+  // The default skin for the application
+  defaultSkin: "classic/1.0",
+  // The current skin used by the application
+  currentSkin: null,
+  // The selected skin to be used by the application when it is restarted. This
+  // will be the same as currentSkin when it is the skin to be used when the
+  // application is restarted
+  selectedSkin: null,
+  // The value of the minCompatibleAppVersion preference
+  minCompatibleAppVersion: null,
+  // The value of the minCompatiblePlatformVersion preference
+  minCompatiblePlatformVersion: null,
+  // A dictionary of the file descriptors for bootstrappable add-ons by ID
+  bootstrappedAddons: {},
+  // A Map of active addons to their bootstrapScope by ID
+  activeAddons: new Map(),
+  // True if the platform could have activated extensions
+  extensionsActive: false,
+  // True if all of the add-ons found during startup were installed in the
+  // application install location
+  allAppGlobal: true,
+  // A string listing the enabled add-ons for annotating crash reports
+  enabledAddons: null,
+  // Keep track of startup phases for telemetry
+  runPhase: XPI_STARTING,
+  // Keep track of the newest file in each add-on, in case we want to
+  // report it to telemetry.
+  _mostRecentlyModifiedFile: {},
+  // Per-addon telemetry information
+  _telemetryDetails: {},
+  // A Map from an add-on install to its ID
+  _addonFileMap: new Map(),
+  // Flag to know if ToolboxProcess.jsm has already been loaded by someone or not
+  _toolboxProcessLoaded: false,
+  // Have we started shutting down bootstrap add-ons?
+  _closing: false,
+
+  /**
+   * Returns an array of the add-on values in `bootstrappedAddons`,
+   * sorted so that all of an add-on's dependencies appear in the array
+   * before itself.
+   *
+   * @returns {Array<object>}
+   *   A sorted array of add-on objects. Each value is a copy of the
+   *   corresponding value in the `bootstrappedAddons` object, with an
+   *   additional `id` property, which corresponds to the key in that
+   *   object, which is the same as the add-ons ID.
+   */
+  sortBootstrappedAddons: function() {
+    let addons = {};
+
+    // Sort the list of IDs so that the ordering is deterministic.
+    for (let id of Object.keys(this.bootstrappedAddons).sort()) {
+      addons[id] = Object.assign({id}, this.bootstrappedAddons[id]);
+    }
+
+    let res = new Set();
+    let seen = new Set();
+
+    let add = addon => {
+      seen.add(addon.id);
+
+      for (let id of addon.dependencies || []) {
+        if (id in addons && !seen.has(id)) {
+          add(addons[id]);
+        }
+      }
+
+      res.add(addon.id);
+    }
+
+    Object.values(addons).forEach(add);
+
+    return Array.from(res, id => addons[id]);
+  },
+
+  /*
+   * Set a value in the telemetry hash for a given ID
+   */
+  setTelemetry: function(aId, aName, aValue) {
+    if (!this._telemetryDetails[aId])
+      this._telemetryDetails[aId] = {};
+    this._telemetryDetails[aId][aName] = aValue;
+  },
+
+  // Keep track of in-progress operations that support cancel()
+  _inProgress: [],
+
+  doing: function(aCancellable) {
+    this._inProgress.push(aCancellable);
+  },
+
+  done: function(aCancellable) {
+    let i = this._inProgress.indexOf(aCancellable);
+    if (i != -1) {
+      this._inProgress.splice(i, 1);
+      return true;
+    }
+    return false;
+  },
+
+  cancelAll: function() {
+    // Cancelling one may alter _inProgress, so don't use a simple iterator
+    while (this._inProgress.length > 0) {
+      let c = this._inProgress.shift();
+      try {
+        c.cancel();
+      }
+      catch (e) {
+        logger.warn("Cancel failed", e);
+      }
+    }
+  },
+
+  /**
+   * Adds or updates a URI mapping for an Addon.id.
+   *
+   * Mappings should not be removed at any point. This is so that the mappings
+   * will be still valid after an add-on gets disabled or uninstalled, as
+   * consumers may still have URIs of (leaked) resources they want to map.
+   */
+  _addURIMapping: function(aID, aFile) {
+    logger.info("Mapping " + aID + " to " + aFile.path);
+    this._addonFileMap.set(aID, aFile.path);
+
+    AddonPathService.insertPath(aFile.path, aID);
+  },
+
+  /**
+   * Resolve a URI back to physical file.
+   *
+   * Of course, this works only for URIs pointing to local resources.
+   *
+   * @param  aURI
+   *         URI to resolve
+   * @return
+   *         resolved nsIFileURL
+   */
+  _resolveURIToFile: function(aURI) {
+    switch (aURI.scheme) {
+      case "jar":
+      case "file":
+        if (aURI instanceof Ci.nsIJARURI) {
+          return this._resolveURIToFile(aURI.JARFile);
+        }
+        return aURI;
+
+      case "chrome":
+        aURI = ChromeRegistry.convertChromeURL(aURI);
+        return this._resolveURIToFile(aURI);
+
+      case "resource":
+        aURI = Services.io.newURI(ResProtocolHandler.resolveURI(aURI), null,
+                                  null);
+        return this._resolveURIToFile(aURI);
+
+      case "view-source":
+        aURI = Services.io.newURI(aURI.path, null, null);
+        return this._resolveURIToFile(aURI);
+
+      case "about":
+        if (aURI.spec == "about:blank") {
+          // Do not attempt to map about:blank
+          return null;
+        }
+
+        let chan;
+        try {
+          chan = NetUtil.newChannel({
+            uri: aURI,
+            loadUsingSystemPrincipal: true
+          });
+        }
+        catch (ex) {
+          return null;
+        }
+        // Avoid looping
+        if (chan.URI.equals(aURI)) {
+          return null;
+        }
+        // We want to clone the channel URI to avoid accidentially keeping
+        // unnecessary references to the channel or implementation details
+        // around.
+        return this._resolveURIToFile(chan.URI.clone());
+
+      default:
+        return null;
+    }
+  },
+
+  /**
+   * Starts the XPI provider initializes the install locations and prefs.
+   *
+   * @param  aAppChanged
+   *         A tri-state value. Undefined means the current profile was created
+   *         for this session, true means the profile already existed but was
+   *         last used with an application with a different version number,
+   *         false means that the profile was last used by this version of the
+   *         application.
+   * @param  aOldAppVersion
+   *         The version of the application last run with this profile or null
+   *         if it is a new profile or the version is unknown
+   * @param  aOldPlatformVersion
+   *         The version of the platform last run with this profile or null
+   *         if it is a new profile or the version is unknown
+   */
+  startup: function(aAppChanged, aOldAppVersion, aOldPlatformVersion) {
+    function addDirectoryInstallLocation(aName, aKey, aPaths, aScope, aLocked) {
+      try {
+        var dir = FileUtils.getDir(aKey, aPaths);
+      }
+      catch (e) {
+        // Some directories aren't defined on some platforms, ignore them
+        logger.debug("Skipping unavailable install location " + aName);
+        return;
+      }
+
+      try {
+        var location = aLocked ? new DirectoryInstallLocation(aName, dir, aScope)
+                               : new MutableDirectoryInstallLocation(aName, dir, aScope);
+      }
+      catch (e) {
+        logger.warn("Failed to add directory install location " + aName, e);
+        return;
+      }
+
+      XPIProvider.installLocations.push(location);
+      XPIProvider.installLocationsByName[location.name] = location;
+    }
+
+    function addSystemAddonInstallLocation(aName, aKey, aPaths, aScope) {
+      try {
+        var dir = FileUtils.getDir(aKey, aPaths);
+      }
+      catch (e) {
+        // Some directories aren't defined on some platforms, ignore them
+        logger.debug("Skipping unavailable install location " + aName);
+        return;
+      }
+
+      try {
+        var location = new SystemAddonInstallLocation(aName, dir, aScope, aAppChanged !== false);
+      }
+      catch (e) {
+        logger.warn("Failed to add system add-on install location " + aName, e);
+        return;
+      }
+
+      XPIProvider.installLocations.push(location);
+      XPIProvider.installLocationsByName[location.name] = location;
+    }
+
+    function addRegistryInstallLocation(aName, aRootkey, aScope) {
+      try {
+        var location = new WinRegInstallLocation(aName, aRootkey, aScope);
+      }
+      catch (e) {
+        logger.warn("Failed to add registry install location " + aName, e);
+        return;
+      }
+
+      XPIProvider.installLocations.push(location);
+      XPIProvider.installLocationsByName[location.name] = location;
+    }
+
+    try {
+      AddonManagerPrivate.recordTimestamp("XPI_startup_begin");
+
+      logger.debug("startup");
+      this.runPhase = XPI_STARTING;
+      this.installs = new Set();
+      this.installLocations = [];
+      this.installLocationsByName = {};
+      // Hook for tests to detect when saving database at shutdown time fails
+      this._shutdownError = null;
+      // Clear this at startup for xpcshell test restarts
+      this._telemetryDetails = {};
+      // Register our details structure with AddonManager
+      AddonManagerPrivate.setTelemetryDetails("XPI", this._telemetryDetails);
+
+      let hasRegistry = ("nsIWindowsRegKey" in Ci);
+
+      let enabledScopes = Preferences.get(PREF_EM_ENABLED_SCOPES,
+                                          AddonManager.SCOPE_ALL);
+
+      // These must be in order of priority, highest to lowest,
+      // for processFileChanges etc. to work
+
+      XPIProvider.installLocations.push(TemporaryInstallLocation);
+      XPIProvider.installLocationsByName[TemporaryInstallLocation.name] =
+        TemporaryInstallLocation;
+
+      // The profile location is always enabled
+      addDirectoryInstallLocation(KEY_APP_PROFILE, KEY_PROFILEDIR,
+                                  [DIR_EXTENSIONS],
+                                  AddonManager.SCOPE_PROFILE, false);
+
+      addSystemAddonInstallLocation(KEY_APP_SYSTEM_ADDONS, KEY_PROFILEDIR,
+                                    [DIR_SYSTEM_ADDONS],
+                                    AddonManager.SCOPE_PROFILE);
+
+      addDirectoryInstallLocation(KEY_APP_SYSTEM_DEFAULTS, KEY_APP_FEATURES,
+                                  [], AddonManager.SCOPE_PROFILE, true);
+
+      if (enabledScopes & AddonManager.SCOPE_USER) {
+        addDirectoryInstallLocation(KEY_APP_SYSTEM_USER, "XREUSysExt",
+                                    [Services.appinfo.ID],
+                                    AddonManager.SCOPE_USER, true);
+        if (hasRegistry) {
+          addRegistryInstallLocation("winreg-app-user",
+                                     Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+                                     AddonManager.SCOPE_USER);
+        }
+      }
+
+      addDirectoryInstallLocation(KEY_APP_GLOBAL, KEY_ADDON_APP_DIR,
+                                  [DIR_EXTENSIONS],
+                                  AddonManager.SCOPE_APPLICATION, true);
+
+      if (enabledScopes & AddonManager.SCOPE_SYSTEM) {
+        addDirectoryInstallLocation(KEY_APP_SYSTEM_SHARE, "XRESysSExtPD",
+                                    [Services.appinfo.ID],
+                                    AddonManager.SCOPE_SYSTEM, true);
+        addDirectoryInstallLocation(KEY_APP_SYSTEM_LOCAL, "XRESysLExtPD",
+                                    [Services.appinfo.ID],
+                                    AddonManager.SCOPE_SYSTEM, true);
+        if (hasRegistry) {
+          addRegistryInstallLocation("winreg-app-global",
+                                     Ci.nsIWindowsRegKey.ROOT_KEY_LOCAL_MACHINE,
+                                     AddonManager.SCOPE_SYSTEM);
+        }
+      }
+
+      let defaultPrefs = new Preferences({ defaultBranch: true });
+      this.defaultSkin = defaultPrefs.get(PREF_GENERAL_SKINS_SELECTEDSKIN,
+                                          "classic/1.0");
+      this.currentSkin = Preferences.get(PREF_GENERAL_SKINS_SELECTEDSKIN,
+                                         this.defaultSkin);
+      this.selectedSkin = this.currentSkin;
+      this.applyThemeChange();
+
+      this.minCompatibleAppVersion = Preferences.get(PREF_EM_MIN_COMPAT_APP_VERSION,
+                                                     null);
+      this.minCompatiblePlatformVersion = Preferences.get(PREF_EM_MIN_COMPAT_PLATFORM_VERSION,
+                                                          null);
+      this.enabledAddons = "";
+
+      Services.prefs.addObserver(PREF_EM_MIN_COMPAT_APP_VERSION, this, false);
+      Services.prefs.addObserver(PREF_EM_MIN_COMPAT_PLATFORM_VERSION, this, false);
+      Services.prefs.addObserver(PREF_E10S_ADDON_BLOCKLIST, this, false);
+      Services.prefs.addObserver(PREF_E10S_ADDON_POLICY, this, false);
+      if (!REQUIRE_SIGNING)
+        Services.prefs.addObserver(PREF_XPI_SIGNATURES_REQUIRED, this, false);
+      Services.obs.addObserver(this, NOTIFICATION_FLUSH_PERMISSIONS, false);
+
+      // Cu.isModuleLoaded can fail here for external XUL apps where there is
+      // no chrome.manifest that defines resource://devtools.
+      if (ResProtocolHandler.hasSubstitution("devtools")) {
+        if (Cu.isModuleLoaded("resource://devtools/client/framework/ToolboxProcess.jsm")) {
+          // If BrowserToolboxProcess is already loaded, set the boolean to true
+          // and do whatever is needed
+          this._toolboxProcessLoaded = true;
+          BrowserToolboxProcess.on("connectionchange",
+                                   this.onDebugConnectionChange.bind(this));
+        } else {
+          // Else, wait for it to load
+          Services.obs.addObserver(this, NOTIFICATION_TOOLBOXPROCESS_LOADED, false);
+        }
+      }
+
+      let flushCaches = this.checkForChanges(aAppChanged, aOldAppVersion,
+                                             aOldPlatformVersion);
+
+      // Changes to installed extensions may have changed which theme is selected
+      this.applyThemeChange();
+
+      AddonManagerPrivate.markProviderSafe(this);
+
+      if (aAppChanged && !this.allAppGlobal &&
+          Preferences.get(PREF_EM_SHOW_MISMATCH_UI, true)) {
+        let addonsToUpdate = this.shouldForceUpdateCheck(aAppChanged);
+        if (addonsToUpdate) {
+          this.showUpgradeUI(addonsToUpdate);
+          flushCaches = true;
+        }
+      }
+
+      if (flushCaches) {
+        Services.obs.notifyObservers(null, "startupcache-invalidate", null);
+        // UI displayed early in startup (like the compatibility UI) may have
+        // caused us to cache parts of the skin or locale in memory. These must
+        // be flushed to allow extension provided skins and locales to take full
+        // effect
+        Services.obs.notifyObservers(null, "chrome-flush-skin-caches", null);
+        Services.obs.notifyObservers(null, "chrome-flush-caches", null);
+      }
+
+      this.enabledAddons = Preferences.get(PREF_EM_ENABLED_ADDONS, "");
+
+      if ("nsICrashReporter" in Ci &&
+          Services.appinfo instanceof Ci.nsICrashReporter) {
+        // Annotate the crash report with relevant add-on information.
+        try {
+          Services.appinfo.annotateCrashReport("Theme", this.currentSkin);
+        } catch (e) { }
+        try {
+          Services.appinfo.annotateCrashReport("EMCheckCompatibility",
+                                               AddonManager.checkCompatibility);
+        } catch (e) { }
+        this.addAddonsToCrashReporter();
+      }
+
+      try {
+        AddonManagerPrivate.recordTimestamp("XPI_bootstrap_addons_begin");
+
+        for (let addon of this.sortBootstrappedAddons()) {
+          try {
+            let file = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+            file.persistentDescriptor = addon.descriptor;
+            let reason = BOOTSTRAP_REASONS.APP_STARTUP;
+            // Eventually set INSTALLED reason when a bootstrap addon
+            // is dropped in profile folder and automatically installed
+            if (AddonManager.getStartupChanges(AddonManager.STARTUP_CHANGE_INSTALLED)
+                            .indexOf(addon.id) !== -1)
+              reason = BOOTSTRAP_REASONS.ADDON_INSTALL;
+            this.callBootstrapMethod(createAddonDetails(addon.id, addon),
+                                     file, "startup", reason);
+          }
+          catch (e) {
+            logger.error("Failed to load bootstrap addon " + addon.id + " from " +
+                         addon.descriptor, e);
+          }
+        }
+        AddonManagerPrivate.recordTimestamp("XPI_bootstrap_addons_end");
+      }
+      catch (e) {
+        logger.error("bootstrap startup failed", e);
+        AddonManagerPrivate.recordException("XPI-BOOTSTRAP", "startup failed", e);
+      }
+
+      // Let these shutdown a little earlier when they still have access to most
+      // of XPCOM
+      Services.obs.addObserver({
+        observe: function(aSubject, aTopic, aData) {
+          XPIProvider._closing = true;
+          for (let addon of XPIProvider.sortBootstrappedAddons().reverse()) {
+            // If no scope has been loaded for this add-on then there is no need
+            // to shut it down (should only happen when a bootstrapped add-on is
+            // pending enable)
+            if (!XPIProvider.activeAddons.has(addon.id))
+              continue;
+
+            let file = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+            file.persistentDescriptor = addon.descriptor;
+            let addonDetails = createAddonDetails(addon.id, addon);
+
+            // If the add-on was pending disable then shut it down and remove it
+            // from the persisted data.
+            if (addon.disable) {
+              XPIProvider.callBootstrapMethod(addonDetails, file, "shutdown",
+                                              BOOTSTRAP_REASONS.ADDON_DISABLE);
+              delete XPIProvider.bootstrappedAddons[addon.id];
+            }
+            else {
+              XPIProvider.callBootstrapMethod(addonDetails, file, "shutdown",
+                                              BOOTSTRAP_REASONS.APP_SHUTDOWN);
+            }
+          }
+          Services.obs.removeObserver(this, "quit-application-granted");
+        }
+      }, "quit-application-granted", false);
+
+      // Detect final-ui-startup for telemetry reporting
+      Services.obs.addObserver({
+        observe: function(aSubject, aTopic, aData) {
+          AddonManagerPrivate.recordTimestamp("XPI_finalUIStartup");
+          XPIProvider.runPhase = XPI_AFTER_UI_STARTUP;
+          Services.obs.removeObserver(this, "final-ui-startup");
+        }
+      }, "final-ui-startup", false);
+
+      AddonManagerPrivate.recordTimestamp("XPI_startup_end");
+
+      this.extensionsActive = true;
+      this.runPhase = XPI_BEFORE_UI_STARTUP;
+
+      let timerManager = Cc["@mozilla.org/updates/timer-manager;1"].
+                         getService(Ci.nsIUpdateTimerManager);
+      timerManager.registerTimer("xpi-signature-verification", () => {
+        this.verifySignatures();
+      }, XPI_SIGNATURE_CHECK_PERIOD);
+    }
+    catch (e) {
+      logger.error("startup failed", e);
+      AddonManagerPrivate.recordException("XPI", "startup failed", e);
+    }
+  },
+
+  /**
+   * Shuts down the database and releases all references.
+   * Return: Promise{integer} resolves / rejects with the result of
+   *                          flushing the XPI Database if it was loaded,
+   *                          0 otherwise.
+   */
+  shutdown: function() {
+    logger.debug("shutdown");
+
+    // Stop anything we were doing asynchronously
+    this.cancelAll();
+
+    this.bootstrappedAddons = {};
+    this.activeAddons.clear();
+    this.enabledAddons = null;
+    this.allAppGlobal = true;
+
+    // If there are pending operations then we must update the list of active
+    // add-ons
+    if (Preferences.get(PREF_PENDING_OPERATIONS, false)) {
+      AddonManagerPrivate.recordSimpleMeasure("XPIDB_pending_ops", 1);
+      XPIDatabase.updateActiveAddons();
+      Services.prefs.setBoolPref(PREF_PENDING_OPERATIONS,
+                                 !XPIDatabase.writeAddonsList());
+    }
+
+    this.installs = null;
+    this.installLocations = null;
+    this.installLocationsByName = null;
+
+    // This is needed to allow xpcshell tests to simulate a restart
+    this.extensionsActive = false;
+    this._addonFileMap.clear();
+
+    if (gLazyObjectsLoaded) {
+      let done = XPIDatabase.shutdown();
+      done.then(
+        ret => {
+          logger.debug("Notifying XPI shutdown observers");
+          Services.obs.notifyObservers(null, "xpi-provider-shutdown", null);
+        },
+        err => {
+          logger.debug("Notifying XPI shutdown observers");
+          this._shutdownError = err;
+          Services.obs.notifyObservers(null, "xpi-provider-shutdown", err);
+        }
+      );
+      return done;
+    }
+    logger.debug("Notifying XPI shutdown observers");
+    Services.obs.notifyObservers(null, "xpi-provider-shutdown", null);
+    return undefined;
+  },
+
+  /**
+   * Applies any pending theme change to the preferences.
+   */
+  applyThemeChange: function() {
+    if (!Preferences.get(PREF_DSS_SWITCHPENDING, false))
+      return;
+
+    // Tell the Chrome Registry which Skin to select
+    try {
+      this.selectedSkin = Preferences.get(PREF_DSS_SKIN_TO_SELECT);
+      Services.prefs.setCharPref(PREF_GENERAL_SKINS_SELECTEDSKIN,
+                                 this.selectedSkin);
+      Services.prefs.clearUserPref(PREF_DSS_SKIN_TO_SELECT);
+      logger.debug("Changed skin to " + this.selectedSkin);
+      this.currentSkin = this.selectedSkin;
+    }
+    catch (e) {
+      logger.error("Error applying theme change", e);
+    }
+    Services.prefs.clearUserPref(PREF_DSS_SWITCHPENDING);
+  },
+
+  /**
+   * If the application has been upgraded and there are add-ons outside the
+   * application directory then we may need to synchronize compatibility
+   * information but only if the mismatch UI isn't disabled.
+   *
+   * @returns False if no update check is needed, otherwise an array of add-on
+   *          IDs to check for updates. Array may be empty if no add-ons can be/need
+   *           to be updated, but the metadata check needs to be performed.
+   */
+  shouldForceUpdateCheck: function(aAppChanged) {
+    AddonManagerPrivate.recordSimpleMeasure("XPIDB_metadata_age", AddonRepository.metadataAge());
+
+    let startupChanges = AddonManager.getStartupChanges(AddonManager.STARTUP_CHANGE_DISABLED);
+    logger.debug("shouldForceUpdateCheck startupChanges: " + startupChanges.toSource());
+    AddonManagerPrivate.recordSimpleMeasure("XPIDB_startup_disabled", startupChanges.length);
+
+    let forceUpdate = [];
+    if (startupChanges.length > 0) {
+    let addons = XPIDatabase.getAddons();
+      for (let addon of addons) {
+        if ((startupChanges.indexOf(addon.id) != -1) &&
+            (addon.permissions() & AddonManager.PERM_CAN_UPGRADE) &&
+            !addon.isCompatible) {
+          logger.debug("shouldForceUpdateCheck: can upgrade disabled add-on " + addon.id);
+          forceUpdate.push(addon.id);
+        }
+      }
+    }
+
+    if (AddonRepository.isMetadataStale()) {
+      logger.debug("shouldForceUpdateCheck: metadata is stale");
+      return forceUpdate;
+    }
+    if (forceUpdate.length > 0) {
+      return forceUpdate;
+    }
+
+    return false;
+  },
+
+  /**
+   * Shows the "Compatibility Updates" UI.
+   *
+   * @param  aAddonIDs
+   *         Array opf addon IDs that were disabled by the application update, and
+   *         should therefore be checked for updates.
+   */
+  showUpgradeUI: function(aAddonIDs) {
+    logger.debug("XPI_showUpgradeUI: " + aAddonIDs.toSource());
+    Services.telemetry.getHistogramById("ADDON_MANAGER_UPGRADE_UI_SHOWN").add(1);
+
+    // Flip a flag to indicate that we interrupted startup with an interactive prompt
+    Services.startup.interrupted = true;
+
+    var variant = Cc["@mozilla.org/variant;1"].
+                  createInstance(Ci.nsIWritableVariant);
+    variant.setFromVariant(aAddonIDs);
+
+    // This *must* be modal as it has to block startup.
+    var features = "chrome,centerscreen,dialog,titlebar,modal";
+    var ww = Cc["@mozilla.org/embedcomp/window-watcher;1"].
+             getService(Ci.nsIWindowWatcher);
+    ww.openWindow(null, URI_EXTENSION_UPDATE_DIALOG, "", features, variant);
+
+    // Ensure any changes to the add-ons list are flushed to disk
+    Services.prefs.setBoolPref(PREF_PENDING_OPERATIONS,
+                               !XPIDatabase.writeAddonsList());
+  },
+
+  updateSystemAddons: Task.async(function*() {
+    let systemAddonLocation = XPIProvider.installLocationsByName[KEY_APP_SYSTEM_ADDONS];
+    if (!systemAddonLocation)
+      return;
+
+    // Don't do anything in safe mode
+    if (Services.appinfo.inSafeMode)
+      return;
+
+    // Download the list of system add-ons
+    let url = Preferences.get(PREF_SYSTEM_ADDON_UPDATE_URL, null);
+    if (!url) {
+      yield systemAddonLocation.cleanDirectories();
+      return;
+    }
+
+    url = UpdateUtils.formatUpdateURL(url);
+
+    logger.info(`Starting system add-on update check from ${url}.`);
+    let res = yield ProductAddonChecker.getProductAddonList(url);
+
+    // If there was no list then do nothing.
+    if (!res || !res.gmpAddons) {
+      logger.info("No system add-ons list was returned.");
+      yield systemAddonLocation.cleanDirectories();
+      return;
+    }
+
+    let addonList = new Map(
+      res.gmpAddons.map(spec => [spec.id, { spec, path: null, addon: null }]));
+
+    let getAddonsInLocation = (location) => {
+      return new Promise(resolve => {
+        XPIDatabase.getAddonsInLocation(location, resolve);
+      });
+    };
+
+    let setMatches = (wanted, existing) => {
+      if (wanted.size != existing.size)
+        return false;
+
+      for (let [id, addon] of existing) {
+        let wantedInfo = wanted.get(id);
+
+        if (!wantedInfo)
+          return false;
+        if (wantedInfo.spec.version != addon.version)
+          return false;
+      }
+
+      return true;
+    };
+
+    // If this matches the current set in the profile location then do nothing.
+    let updatedAddons = addonMap(yield getAddonsInLocation(KEY_APP_SYSTEM_ADDONS));
+    if (setMatches(addonList, updatedAddons)) {
+      logger.info("Retaining existing updated system add-ons.");
+      yield systemAddonLocation.cleanDirectories();
+      return;
+    }
+
+    // If this matches the current set in the default location then reset the
+    // updated set.
+    let defaultAddons = addonMap(yield getAddonsInLocation(KEY_APP_SYSTEM_DEFAULTS));
+    if (setMatches(addonList, defaultAddons)) {
+      logger.info("Resetting system add-ons.");
+      systemAddonLocation.resetAddonSet();
+      yield systemAddonLocation.cleanDirectories();
+      return;
+    }
+
+    // Download all the add-ons
+    let downloadAddon = Task.async(function*(item) {
+      try {
+        let sourceAddon = updatedAddons.get(item.spec.id);
+        if (sourceAddon && sourceAddon.version == item.spec.version) {
+          // Copying the file to a temporary location has some benefits. If the
+          // file is locked and cannot be read then we'll fall back to
+          // downloading a fresh copy. It also means we don't have to remember
+          // whether to delete the temporary copy later.
+          try {
+            let path = OS.Path.join(OS.Constants.Path.tmpDir, "tmpaddon");
+            let unique = yield OS.File.openUnique(path);
+            unique.file.close();
+            yield OS.File.copy(sourceAddon._sourceBundle.path, unique.path);
+            // Make sure to update file modification times so this is detected
+            // as a new add-on.
+            yield OS.File.setDates(unique.path);
+            item.path = unique.path;
+          }
+          catch (e) {
+            logger.warn(`Failed make temporary copy of ${sourceAddon._sourceBundle.path}.`, e);
+          }
+        }
+        if (!item.path) {
+          item.path = yield ProductAddonChecker.downloadAddon(item.spec);
+        }
+        item.addon = yield loadManifestFromFile(nsIFile(item.path), systemAddonLocation);
+      }
+      catch (e) {
+        logger.error(`Failed to download system add-on ${item.spec.id}`, e);
+      }
+    });
+    yield Promise.all(Array.from(addonList.values()).map(downloadAddon));
+
+    // The download promises all resolve regardless, now check if they all
+    // succeeded
+    let validateAddon = (item) => {
+      if (item.spec.id != item.addon.id) {
+        logger.warn(`Downloaded system add-on expected to be ${item.spec.id} but was ${item.addon.id}.`);
+        return false;
+      }
+
+      if (item.spec.version != item.addon.version) {
+        logger.warn(`Expected system add-on ${item.spec.id} to be version ${item.spec.version} but was ${item.addon.version}.`);
+        return false;
+      }
+
+      if (!systemAddonLocation.isValidAddon(item.addon))
+        return false;
+
+      return true;
+    }
+
+    if (!Array.from(addonList.values()).every(item => item.path && item.addon && validateAddon(item))) {
+      throw new Error("Rejecting updated system add-on set that either could not " +
+                      "be downloaded or contained unusable add-ons.");
+    }
+
+    // Install into the install location
+    logger.info("Installing new system add-on set");
+    yield systemAddonLocation.installAddonSet(Array.from(addonList.values())
+      .map(a => a.addon));
+  }),
+
+  /**
+   * Verifies that all installed add-ons are still correctly signed.
+   */
+  verifySignatures: function() {
+    XPIDatabase.getAddonList(a => true, (addons) => {
+      Task.spawn(function*() {
+        let changes = {
+          enabled: [],
+          disabled: []
+        };
+
+        for (let addon of addons) {
+          // The add-on might have vanished, we'll catch that on the next startup
+          if (!addon._sourceBundle.exists())
+            continue;
+
+          let signedState = yield verifyBundleSignedState(addon._sourceBundle, addon);
+
+          if (signedState != addon.signedState) {
+            addon.signedState = signedState;
+            AddonManagerPrivate.callAddonListeners("onPropertyChanged",
+                                                   addon.wrapper,
+                                                   ["signedState"]);
+          }
+
+          let disabled = XPIProvider.updateAddonDisabledState(addon);
+          if (disabled !== undefined)
+            changes[disabled ? "disabled" : "enabled"].push(addon.id);
+        }
+
+        XPIDatabase.saveChanges();
+
+        Services.obs.notifyObservers(null, "xpi-signature-changed", JSON.stringify(changes));
+      }).then(null, err => {
+        logger.error("XPI_verifySignature: " + err);
+      })
+    });
+  },
+
+  /**
+   * Persists changes to XPIProvider.bootstrappedAddons to its store (a pref).
+   */
+  persistBootstrappedAddons: function() {
+    // Experiments are disabled upon app load, so don't persist references.
+    let filtered = {};
+    for (let id in this.bootstrappedAddons) {
+      let entry = this.bootstrappedAddons[id];
+      if (entry.type == "experiment") {
+        continue;
+      }
+
+      filtered[id] = entry;
+    }
+
+    Services.prefs.setCharPref(PREF_BOOTSTRAP_ADDONS,
+                               JSON.stringify(filtered));
+  },
+
+  /**
+   * Adds a list of currently active add-ons to the next crash report.
+   */
+  addAddonsToCrashReporter: function() {
+    if (!("nsICrashReporter" in Ci) ||
+        !(Services.appinfo instanceof Ci.nsICrashReporter))
+      return;
+
+    // In safe mode no add-ons are loaded so we should not include them in the
+    // crash report
+    if (Services.appinfo.inSafeMode)
+      return;
+
+    let data = this.enabledAddons;
+    for (let id in this.bootstrappedAddons) {
+      data += (data ? "," : "") + encodeURIComponent(id) + ":" +
+              encodeURIComponent(this.bootstrappedAddons[id].version);
+    }
+
+    try {
+      Services.appinfo.annotateCrashReport("Add-ons", data);
+    }
+    catch (e) { }
+
+    let TelemetrySession =
+      Cu.import("resource://gre/modules/TelemetrySession.jsm", {}).TelemetrySession;
+    TelemetrySession.setAddOns(data);
+  },
+
+  /**
+   * Check the staging directories of install locations for any add-ons to be
+   * installed or add-ons to be uninstalled.
+   *
+   * @param  aManifests
+   *         A dictionary to add detected install manifests to for the purpose
+   *         of passing through updated compatibility information
+   * @return true if an add-on was installed or uninstalled
+   */
+  processPendingFileChanges: function(aManifests) {
+    let changed = false;
+    for (let location of this.installLocations) {
+      aManifests[location.name] = {};
+      // We can't install or uninstall anything in locked locations
+      if (location.locked) {
+        continue;
+      }
+
+      let stagingDir = location.getStagingDir();
+
+      try {
+        if (!stagingDir || !stagingDir.exists() || !stagingDir.isDirectory())
+          continue;
+      }
+      catch (e) {
+        logger.warn("Failed to find staging directory", e);
+        continue;
+      }
+
+      let seenFiles = [];
+      // Use a snapshot of the directory contents to avoid possible issues with
+      // iterating over a directory while removing files from it (the YAFFS2
+      // embedded filesystem has this issue, see bug 772238), and to remove
+      // normal files before their resource forks on OSX (see bug 733436).
+      let stagingDirEntries = getDirectoryEntries(stagingDir, true);
+      for (let stageDirEntry of stagingDirEntries) {
+        let id = stageDirEntry.leafName;
+
+        let isDir;
+        try {
+          isDir = stageDirEntry.isDirectory();
+        }
+        catch (e) {
+          if (e.result != Cr.NS_ERROR_FILE_TARGET_DOES_NOT_EXIST)
+            throw e;
+          // If the file has already gone away then don't worry about it, this
+          // can happen on OSX where the resource fork is automatically moved
+          // with the data fork for the file. See bug 733436.
+          continue;
+        }
+
+        if (!isDir) {
+          if (id.substring(id.length - 4).toLowerCase() == ".xpi") {
+            id = id.substring(0, id.length - 4);
+          }
+          else {
+            if (id.substring(id.length - 5).toLowerCase() != ".json") {
+              logger.warn("Ignoring file: " + stageDirEntry.path);
+              seenFiles.push(stageDirEntry.leafName);
+            }
+            continue;
+          }
+        }
+
+        // Check that the directory's name is a valid ID.
+        if (!gIDTest.test(id)) {
+          logger.warn("Ignoring directory whose name is not a valid add-on ID: " +
+               stageDirEntry.path);
+          seenFiles.push(stageDirEntry.leafName);
+          continue;
+        }
+
+        changed = true;
+
+        if (isDir) {
+          // Check if the directory contains an install manifest.
+          let manifest = getManifestFileForDir(stageDirEntry);
+
+          // If the install manifest doesn't exist uninstall this add-on in this
+          // install location.
+          if (!manifest) {
+            logger.debug("Processing uninstall of " + id + " in " + location.name);
+
+            try {
+              let addonFile = location.getLocationForID(id);
+              let addonToUninstall = syncLoadManifestFromFile(addonFile, location);
+              if (addonToUninstall.bootstrap) {
+                this.callBootstrapMethod(addonToUninstall, addonToUninstall._sourceBundle,
+                                         "uninstall", BOOTSTRAP_REASONS.ADDON_UNINSTALL);
+              }
+            }
+            catch (e) {
+              logger.warn("Failed to call uninstall for " + id, e);
+            }
+
+            try {
+              location.uninstallAddon(id);
+              seenFiles.push(stageDirEntry.leafName);
+            }
+            catch (e) {
+              logger.error("Failed to uninstall add-on " + id + " in " + location.name, e);
+            }
+            // The file check later will spot the removal and cleanup the database
+            continue;
+          }
+        }
+
+        aManifests[location.name][id] = null;
+        let existingAddonID = id;
+
+        let jsonfile = stagingDir.clone();
+        jsonfile.append(id + ".json");
+        // Assume this was a foreign install if there is no cached metadata file
+        let foreignInstall = !jsonfile.exists();
+        let addon;
+
+        try {
+          addon = syncLoadManifestFromFile(stageDirEntry, location);
+        }
+        catch (e) {
+          logger.error("Unable to read add-on manifest from " + stageDirEntry.path, e);
+          // This add-on can't be installed so just remove it now
+          seenFiles.push(stageDirEntry.leafName);
+          seenFiles.push(jsonfile.leafName);
+          continue;
+        }
+
+        if (mustSign(addon.type) &&
+            addon.signedState <= AddonManager.SIGNEDSTATE_MISSING) {
+          logger.warn("Refusing to install staged add-on " + id + " with signed state " + addon.signedState);
+          seenFiles.push(stageDirEntry.leafName);
+          seenFiles.push(jsonfile.leafName);
+          continue;
+        }
+
+        // Check for a cached metadata for this add-on, it may contain updated
+        // compatibility information
+        if (!foreignInstall) {
+          logger.debug("Found updated metadata for " + id + " in " + location.name);
+          let fis = Cc["@mozilla.org/network/file-input-stream;1"].
+                       createInstance(Ci.nsIFileInputStream);
+          let json = Cc["@mozilla.org/dom/json;1"].
+                     createInstance(Ci.nsIJSON);
+
+          try {
+            fis.init(jsonfile, -1, 0, 0);
+            let metadata = json.decodeFromStream(fis, jsonfile.fileSize);
+            addon.importMetadata(metadata);
+
+            // Pass this through to addMetadata so it knows this add-on was
+            // likely installed through the UI
+            aManifests[location.name][id] = addon;
+          }
+          catch (e) {
+            // If some data can't be recovered from the cached metadata then it
+            // is unlikely to be a problem big enough to justify throwing away
+            // the install, just log an error and continue
+            logger.error("Unable to read metadata from " + jsonfile.path, e);
+          }
+          finally {
+            fis.close();
+          }
+        }
+        seenFiles.push(jsonfile.leafName);
+
+        existingAddonID = addon.existingAddonID || id;
+
+        var oldBootstrap = null;
+        logger.debug("Processing install of " + id + " in " + location.name);
+        if (existingAddonID in this.bootstrappedAddons) {
+          try {
+            var existingAddon = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+            existingAddon.persistentDescriptor = this.bootstrappedAddons[existingAddonID].descriptor;
+            if (existingAddon.exists()) {
+              oldBootstrap = this.bootstrappedAddons[existingAddonID];
+
+              // We'll be replacing a currently active bootstrapped add-on so
+              // call its uninstall method
+              let newVersion = addon.version;
+              let oldVersion = oldBootstrap.version;
+              let uninstallReason = Services.vc.compare(oldVersion, newVersion) < 0 ?
+                                    BOOTSTRAP_REASONS.ADDON_UPGRADE :
+                                    BOOTSTRAP_REASONS.ADDON_DOWNGRADE;
+
+              this.callBootstrapMethod(createAddonDetails(existingAddonID, oldBootstrap),
+                                       existingAddon, "uninstall", uninstallReason,
+                                       { newVersion: newVersion });
+              this.unloadBootstrapScope(existingAddonID);
+              flushChromeCaches();
+            }
+          }
+          catch (e) {
+          }
+        }
+
+        try {
+          addon._sourceBundle = location.installAddon({
+            id,
+            source: stageDirEntry,
+            existingAddonID
+          });
+        }
+        catch (e) {
+          logger.error("Failed to install staged add-on " + id + " in " + location.name,
+                e);
+          // Re-create the staged install
+          new StagedAddonInstall(location, stageDirEntry, addon);
+          // Make sure not to delete the cached manifest json file
+          seenFiles.pop();
+
+          delete aManifests[location.name][id];
+
+          if (oldBootstrap) {
+            // Re-install the old add-on
+            this.callBootstrapMethod(createAddonDetails(existingAddonID, oldBootstrap),
+                                     existingAddon, "install",
+                                     BOOTSTRAP_REASONS.ADDON_INSTALL);
+          }
+          continue;
+        }
+      }
+
+      try {
+        location.cleanStagingDir(seenFiles);
+      }
+      catch (e) {
+        // Non-critical, just saves some perf on startup if we clean this up.
+        logger.debug("Error cleaning staging dir " + stagingDir.path, e);
+      }
+    }
+    return changed;
+  },
+
+  /**
+   * Installs any add-ons located in the extensions directory of the
+   * application's distribution specific directory into the profile unless a
+   * newer version already exists or the user has previously uninstalled the
+   * distributed add-on.
+   *
+   * @param  aManifests
+   *         A dictionary to add new install manifests to to save having to
+   *         reload them later
+   * @param  aAppChanged
+   *         See checkForChanges
+   * @return true if any new add-ons were installed
+   */
+  installDistributionAddons: function(aManifests, aAppChanged) {
+    let distroDir;
+    try {
+      distroDir = FileUtils.getDir(KEY_APP_DISTRIBUTION, [DIR_EXTENSIONS]);
+    }
+    catch (e) {
+      return false;
+    }
+
+    if (!distroDir.exists())
+      return false;
+
+    if (!distroDir.isDirectory())
+      return false;
+
+    let changed = false;
+    let profileLocation = this.installLocationsByName[KEY_APP_PROFILE];
+
+    let entries = distroDir.directoryEntries
+                           .QueryInterface(Ci.nsIDirectoryEnumerator);
+    let entry;
+    while ((entry = entries.nextFile)) {
+
+      let id = entry.leafName;
+
+      if (entry.isFile()) {
+        if (id.substring(id.length - 4).toLowerCase() == ".xpi") {
+          id = id.substring(0, id.length - 4);
+        }
+        else {
+          logger.debug("Ignoring distribution add-on that isn't an XPI: " + entry.path);
+          continue;
+        }
+      }
+      else if (!entry.isDirectory()) {
+        logger.debug("Ignoring distribution add-on that isn't a file or directory: " +
+            entry.path);
+        continue;
+      }
+
+      if (!gIDTest.test(id)) {
+        logger.debug("Ignoring distribution add-on whose name is not a valid add-on ID: " +
+            entry.path);
+        continue;
+      }
+
+      /* If this is not an upgrade and we've already handled this extension
+       * just continue */
+      if (!aAppChanged && Preferences.isSet(PREF_BRANCH_INSTALLED_ADDON + id)) {
+        continue;
+      }
+
+      let addon;
+      try {
+        addon = syncLoadManifestFromFile(entry, profileLocation);
+      }
+      catch (e) {
+        logger.warn("File entry " + entry.path + " contains an invalid add-on", e);
+        continue;
+      }
+
+      if (addon.id != id) {
+        logger.warn("File entry " + entry.path + " contains an add-on with an " +
+             "incorrect ID")
+        continue;
+      }
+
+      let existingEntry = null;
+      try {
+        existingEntry = profileLocation.getLocationForID(id);
+      }
+      catch (e) {
+      }
+
+      if (existingEntry) {
+        let existingAddon;
+        try {
+          existingAddon = syncLoadManifestFromFile(existingEntry, profileLocation);
+
+          if (Services.vc.compare(addon.version, existingAddon.version) <= 0)
+            continue;
+        }
+        catch (e) {
+          // Bad add-on in the profile so just proceed and install over the top
+          logger.warn("Profile contains an add-on with a bad or missing install " +
+               "manifest at " + existingEntry.path + ", overwriting", e);
+        }
+      }
+      else if (Preferences.get(PREF_BRANCH_INSTALLED_ADDON + id, false)) {
+        continue;
+      }
+
+      // Install the add-on
+      try {
+        addon._sourceBundle = profileLocation.installAddon({ id, source: entry, action: "copy" });
+        logger.debug("Installed distribution add-on " + id);
+
+        Services.prefs.setBoolPref(PREF_BRANCH_INSTALLED_ADDON + id, true)
+
+        // aManifests may contain a copy of a newly installed add-on's manifest
+        // and we'll have overwritten that so instead cache our install manifest
+        // which will later be put into the database in processFileChanges
+        if (!(KEY_APP_PROFILE in aManifests))
+          aManifests[KEY_APP_PROFILE] = {};
+        aManifests[KEY_APP_PROFILE][id] = addon;
+        changed = true;
+      }
+      catch (e) {
+        logger.error("Failed to install distribution add-on " + entry.path, e);
+      }
+    }
+
+    entries.close();
+
+    return changed;
+  },
+
+  /**
+   * Imports the xpinstall permissions from preferences into the permissions
+   * manager for the user to change later.
+   */
+  importPermissions: function() {
+    PermissionsUtils.importFromPrefs(PREF_XPI_PERMISSIONS_BRANCH,
+                                     XPI_PERMISSION);
+  },
+
+  getDependentAddons: function(aAddon) {
+    return Array.from(XPIDatabase.getAddons())
+                .filter(addon => addon.dependencies.includes(aAddon.id));
+  },
+
+  /**
+   * Checks for any changes that have occurred since the last time the
+   * application was launched.
+   *
+   * @param  aAppChanged
+   *         A tri-state value. Undefined means the current profile was created
+   *         for this session, true means the profile already existed but was
+   *         last used with an application with a different version number,
+   *         false means that the profile was last used by this version of the
+   *         application.
+   * @param  aOldAppVersion
+   *         The version of the application last run with this profile or null
+   *         if it is a new profile or the version is unknown
+   * @param  aOldPlatformVersion
+   *         The version of the platform last run with this profile or null
+   *         if it is a new profile or the version is unknown
+   * @return true if a change requiring a restart was detected
+   */
+  checkForChanges: function(aAppChanged, aOldAppVersion,
+                                                aOldPlatformVersion) {
+    logger.debug("checkForChanges");
+
+    // Keep track of whether and why we need to open and update the database at
+    // startup time.
+    let updateReasons = [];
+    if (aAppChanged) {
+      updateReasons.push("appChanged");
+    }
+
+    // Load the list of bootstrapped add-ons first so processFileChanges can
+    // modify it
+    // XXX eventually get rid of bootstrappedAddons
+    try {
+      this.bootstrappedAddons = JSON.parse(Preferences.get(PREF_BOOTSTRAP_ADDONS,
+                                           "{}"));
+    } catch (e) {
+      logger.warn("Error parsing enabled bootstrapped extensions cache", e);
+    }
+
+    // First install any new add-ons into the locations, if there are any
+    // changes then we must update the database with the information in the
+    // install locations
+    let manifests = {};
+    let updated = this.processPendingFileChanges(manifests);
+    if (updated) {
+      updateReasons.push("pendingFileChanges");
+    }
+
+    // This will be true if the previous session made changes that affect the
+    // active state of add-ons but didn't commit them properly (normally due
+    // to the application crashing)
+    let hasPendingChanges = Preferences.get(PREF_PENDING_OPERATIONS);
+    if (hasPendingChanges) {
+      updateReasons.push("hasPendingChanges");
+    }
+
+    // If the application has changed then check for new distribution add-ons
+    if (Preferences.get(PREF_INSTALL_DISTRO_ADDONS, true))
+    {
+      updated = this.installDistributionAddons(manifests, aAppChanged);
+      if (updated) {
+        updateReasons.push("installDistributionAddons");
+      }
+    }
+
+    // Telemetry probe added around getInstallState() to check perf
+    let telemetryCaptureTime = Cu.now();
+    let installChanged = XPIStates.getInstallState();
+    let telemetry = Services.telemetry;
+    telemetry.getHistogramById("CHECK_ADDONS_MODIFIED_MS").add(Math.round(Cu.now() - telemetryCaptureTime));
+    if (installChanged) {
+      updateReasons.push("directoryState");
+    }
+
+    let haveAnyAddons = (XPIStates.size > 0);
+
+    // If the schema appears to have changed then we should update the database
+    if (DB_SCHEMA != Preferences.get(PREF_DB_SCHEMA, 0)) {
+      // If we don't have any add-ons, just update the pref, since we don't need to
+      // write the database
+      if (!haveAnyAddons) {
+        logger.debug("Empty XPI database, setting schema version preference to " + DB_SCHEMA);
+        Services.prefs.setIntPref(PREF_DB_SCHEMA, DB_SCHEMA);
+      }
+      else {
+        updateReasons.push("schemaChanged");
+      }
+    }
+
+    // If the database doesn't exist and there are add-ons installed then we
+    // must update the database however if there are no add-ons then there is
+    // no need to update the database.
+    let dbFile = FileUtils.getFile(KEY_PROFILEDIR, [FILE_DATABASE], true);
+    if (!dbFile.exists() && haveAnyAddons) {
+      updateReasons.push("needNewDatabase");
+    }
+
+    // XXX This will go away when we fold bootstrappedAddons into XPIStates.
+    if (updateReasons.length == 0) {
+      let bootstrapDescriptors = new Set(Object.keys(this.bootstrappedAddons)
+        .map(b => this.bootstrappedAddons[b].descriptor));
+
+      for (let location of XPIStates.db.values()) {
+        for (let state of location.values()) {
+          bootstrapDescriptors.delete(state.descriptor);
+        }
+      }
+
+      if (bootstrapDescriptors.size > 0) {
+        logger.warn("Bootstrap state is invalid (missing add-ons: "
+            + Array.from(bootstrapDescriptors).join(", ") + ")");
+        updateReasons.push("missingBootstrapAddon");
+      }
+    }
+
+    // Catch and log any errors during the main startup
+    try {
+      let extensionListChanged = false;
+      // If the database needs to be updated then open it and then update it
+      // from the filesystem
+      if (updateReasons.length > 0) {
+        AddonManagerPrivate.recordSimpleMeasure("XPIDB_startup_load_reasons", updateReasons);
+        XPIDatabase.syncLoadDB(false);
+        try {
+          extensionListChanged = XPIDatabaseReconcile.processFileChanges(manifests,
+                                                                         aAppChanged,
+                                                                         aOldAppVersion,
+                                                                         aOldPlatformVersion,
+                                                                         updateReasons.includes("schemaChanged"));
+        }
+        catch (e) {
+          logger.error("Failed to process extension changes at startup", e);
+        }
+      }
+
+      if (aAppChanged) {
+        // When upgrading the app and using a custom skin make sure it is still
+        // compatible otherwise switch back the default
+        if (this.currentSkin != this.defaultSkin) {
+          let oldSkin = XPIDatabase.getVisibleAddonForInternalName(this.currentSkin);
+          if (!oldSkin || oldSkin.disabled)
+            this.enableDefaultTheme();
+        }
+
+        // When upgrading remove the old extensions cache to force older
+        // versions to rescan the entire list of extensions
+        let oldCache = FileUtils.getFile(KEY_PROFILEDIR, [FILE_OLD_CACHE], true);
+        try {
+          if (oldCache.exists())
+            oldCache.remove(true);
+        }
+        catch (e) {
+          logger.warn("Unable to remove old extension cache " + oldCache.path, e);
+        }
+      }
+
+      // If the application crashed before completing any pending operations then
+      // we should perform them now.
+      if (extensionListChanged || hasPendingChanges) {
+        logger.debug("Updating database with changes to installed add-ons");
+        XPIDatabase.updateActiveAddons();
+        Services.prefs.setBoolPref(PREF_PENDING_OPERATIONS,
+                                   !XPIDatabase.writeAddonsList());
+        Services.prefs.setCharPref(PREF_BOOTSTRAP_ADDONS,
+                                   JSON.stringify(this.bootstrappedAddons));
+        return true;
+      }
+
+      logger.debug("No changes found");
+    }
+    catch (e) {
+      logger.error("Error during startup file checks", e);
+    }
+
+    // Check that the add-ons list still exists
+    let addonsList = FileUtils.getFile(KEY_PROFILEDIR, [FILE_XPI_ADDONS_LIST],
+                                       true);
+    // the addons list file should exist if and only if we have add-ons installed
+    if (addonsList.exists() != haveAnyAddons) {
+      logger.debug("Add-ons list is invalid, rebuilding");
+      XPIDatabase.writeAddonsList();
+    }
+
+    return false;
+  },
+
+  /**
+   * Called to test whether this provider supports installing a particular
+   * mimetype.
+   *
+   * @param  aMimetype
+   *         The mimetype to check for
+   * @return true if the mimetype is application/x-xpinstall
+   */
+  supportsMimetype: function(aMimetype) {
+    return aMimetype == "application/x-xpinstall";
+  },
+
+  /**
+   * Called to test whether installing XPI add-ons is enabled.
+   *
+   * @return true if installing is enabled
+   */
+  isInstallEnabled: function() {
+    // Default to enabled if the preference does not exist
+    return Preferences.get(PREF_XPI_ENABLED, true);
+  },
+
+  /**
+   * Called to test whether installing XPI add-ons by direct URL requests is
+   * whitelisted.
+   *
+   * @return true if installing by direct requests is whitelisted
+   */
+  isDirectRequestWhitelisted: function() {
+    // Default to whitelisted if the preference does not exist.
+    return Preferences.get(PREF_XPI_DIRECT_WHITELISTED, true);
+  },
+
+  /**
+   * Called to test whether installing XPI add-ons from file referrers is
+   * whitelisted.
+   *
+   * @return true if installing from file referrers is whitelisted
+   */
+  isFileRequestWhitelisted: function() {
+    // Default to whitelisted if the preference does not exist.
+    return Preferences.get(PREF_XPI_FILE_WHITELISTED, true);
+  },
+
+  /**
+   * Called to test whether installing XPI add-ons from a URI is allowed.
+   *
+   * @param  aInstallingPrincipal
+   *         The nsIPrincipal that initiated the install
+   * @return true if installing is allowed
+   */
+  isInstallAllowed: function(aInstallingPrincipal) {
+    if (!this.isInstallEnabled())
+      return false;
+
+    let uri = aInstallingPrincipal.URI;
+
+    // Direct requests without a referrer are either whitelisted or blocked.
+    if (!uri)
+      return this.isDirectRequestWhitelisted();
+
+    // Local referrers can be whitelisted.
+    if (this.isFileRequestWhitelisted() &&
+        (uri.schemeIs("chrome") || uri.schemeIs("file")))
+      return true;
+
+    this.importPermissions();
+
+    let permission = Services.perms.testPermissionFromPrincipal(aInstallingPrincipal, XPI_PERMISSION);
+    if (permission == Ci.nsIPermissionManager.DENY_ACTION)
+      return false;
+
+    let requireWhitelist = Preferences.get(PREF_XPI_WHITELIST_REQUIRED, true);
+    if (requireWhitelist && (permission != Ci.nsIPermissionManager.ALLOW_ACTION))
+      return false;
+
+    let requireSecureOrigin = Preferences.get(PREF_INSTALL_REQUIRESECUREORIGIN, true);
+    let safeSchemes = ["https", "chrome", "file"];
+    if (requireSecureOrigin && safeSchemes.indexOf(uri.scheme) == -1)
+      return false;
+
+    return true;
+  },
+
+  /**
+   * Called to get an AddonInstall to download and install an add-on from a URL.
+   *
+   * @param  aUrl
+   *         The URL to be installed
+   * @param  aHash
+   *         A hash for the install
+   * @param  aName
+   *         A name for the install
+   * @param  aIcons
+   *         Icon URLs for the install
+   * @param  aVersion
+   *         A version for the install
+   * @param  aBrowser
+   *         The browser performing the install
+   * @param  aCallback
+   *         A callback to pass the AddonInstall to
+   */
+  getInstallForURL: function(aUrl, aHash, aName, aIcons, aVersion, aBrowser,
+                             aCallback) {
+    createDownloadInstall(function(aInstall) {
+      aCallback(aInstall.wrapper);
+    }, aUrl, aHash, aName, aIcons, aVersion, aBrowser);
+  },
+
+  /**
+   * Called to get an AddonInstall to install an add-on from a local file.
+   *
+   * @param  aFile
+   *         The file to be installed
+   * @param  aCallback
+   *         A callback to pass the AddonInstall to
+   */
+  getInstallForFile: function(aFile, aCallback) {
+    createLocalInstall(aFile).then(install => {
+      aCallback(install ? install.wrapper : null);
+    });
+  },
+
+  /**
+   * Temporarily installs add-on from a local XPI file or directory.
+   * As this is intended for development, the signature is not checked and
+   * the add-on does not persist on application restart.
+   *
+   * @param aFile
+   *        An nsIFile for the unpacked add-on directory or XPI file.
+   *
+   * @return See installAddonFromLocation return value.
+   */
+  installTemporaryAddon: function(aFile) {
+    return this.installAddonFromLocation(aFile, TemporaryInstallLocation);
+  },
+
+  /**
+   * Permanently installs add-on from a local XPI file or directory.
+   * The signature is checked but the add-on persist on application restart.
+   *
+   * @param aFile
+   *        An nsIFile for the unpacked add-on directory or XPI file.
+   *
+   * @return See installAddonFromLocation return value.
+   */
+  installAddonFromSources: Task.async(function*(aFile) {
+    let location = XPIProvider.installLocationsByName[KEY_APP_PROFILE];
+    return this.installAddonFromLocation(aFile, location, "proxy");
+  }),
+
+  /**
+   * Installs add-on from a local XPI file or directory.
+   *
+   * @param aFile
+   *        An nsIFile for the unpacked add-on directory or XPI file.
+   * @param aInstallLocation
+   *        Define a custom install location object to use for the install.
+   * @param aInstallAction
+   *        Optional action mode to use when installing the addon
+   *        (see MutableDirectoryInstallLocation.installAddon)
+   *
+   * @return a Promise that resolves to an Addon object on success, or rejects
+   *         if the add-on is not a valid restartless add-on or if the
+   *         same ID is already installed.
+   */
+  installAddonFromLocation: Task.async(function*(aFile, aInstallLocation, aInstallAction) {
+    if (aFile.exists() && aFile.isFile()) {
+      flushJarCache(aFile);
+    }
+    let addon = yield loadManifestFromFile(aFile, aInstallLocation);
+
+    aInstallLocation.installAddon({ id: addon.id, source: aFile, action: aInstallAction });
+
+    if (addon.appDisabled) {
+      let message = `Add-on ${addon.id} is not compatible with application version.`;
+
+      let app = addon.matchingTargetApplication;
+      if (app) {
+        if (app.minVersion) {
+          message += ` add-on minVersion: ${app.minVersion}.`;
+        }
+        if (app.maxVersion) {
+          message += ` add-on maxVersion: ${app.maxVersion}.`;
+        }
+      }
+      throw new Error(message);
+    }
+
+    if (!addon.bootstrap) {
+      throw new Error("Only restartless (bootstrap) add-ons"
+                    + " can be installed from sources:", addon.id);
+    }
+    let installReason = BOOTSTRAP_REASONS.ADDON_INSTALL;
+    let oldAddon = yield new Promise(
+                   resolve => XPIDatabase.getVisibleAddonForID(addon.id, resolve));
+    if (oldAddon) {
+      if (!oldAddon.bootstrap) {
+        logger.warn("Non-restartless Add-on is already installed", addon.id);
+        throw new Error("Non-restartless add-on with ID "
+                        + oldAddon.id + " is already installed");
+      }
+      else {
+        logger.warn("Addon with ID " + oldAddon.id + " already installed,"
+                    + " older version will be disabled");
+
+        let existingAddonID = oldAddon.id;
+        let existingAddon = oldAddon._sourceBundle;
+
+        // We'll be replacing a currently active bootstrapped add-on so
+        // call its uninstall method
+        let newVersion = addon.version;
+        let oldVersion = oldAddon.version;
+        if (Services.vc.compare(newVersion, oldVersion) >= 0) {
+          installReason = BOOTSTRAP_REASONS.ADDON_UPGRADE;
+        } else {
+          installReason = BOOTSTRAP_REASONS.ADDON_DOWNGRADE;
+        }
+        let uninstallReason = installReason;
+
+        if (oldAddon.active) {
+          XPIProvider.callBootstrapMethod(oldAddon, existingAddon,
+                                          "shutdown", uninstallReason,
+                                          { newVersion });
+        }
+        this.callBootstrapMethod(oldAddon, existingAddon,
+                                 "uninstall", uninstallReason, { newVersion });
+        this.unloadBootstrapScope(existingAddonID);
+        flushChromeCaches();
+      }
+    }
+
+    let file = addon._sourceBundle;
+
+    XPIProvider._addURIMapping(addon.id, file);
+    XPIProvider.callBootstrapMethod(addon, file, "install", installReason);
+    addon.state = AddonManager.STATE_INSTALLED;
+    logger.debug("Install of temporary addon in " + aFile.path + " completed.");
+    addon.visible = true;
+    addon.enabled = true;
+    addon.active = true;
+
+    addon = XPIDatabase.addAddonMetadata(addon, file.persistentDescriptor);
+
+    XPIStates.addAddon(addon);
+    XPIDatabase.saveChanges();
+    XPIStates.save();
+
+    AddonManagerPrivate.callAddonListeners("onInstalling", addon.wrapper,
+                                           false);
+    XPIProvider.callBootstrapMethod(addon, file, "startup",
+                                    BOOTSTRAP_REASONS.ADDON_ENABLE);
+    AddonManagerPrivate.callInstallListeners("onExternalInstall",
+                                             null, addon.wrapper,
+                                             oldAddon ? oldAddon.wrapper : null,
+                                             false);
+    AddonManagerPrivate.callAddonListeners("onInstalled", addon.wrapper);
+
+    return addon.wrapper;
+  }),
+
+  /**
+   * Returns an Addon corresponding to an instance ID.
+   * @param aInstanceID
+   *        An Addon Instance ID
+   * @return {Promise}
+   * @resolves The found Addon or null if no such add-on exists.
+   * @rejects  Never
+   * @throws if the aInstanceID argument is not specified
+   */
+   getAddonByInstanceID: function(aInstanceID) {
+     if (!aInstanceID || typeof aInstanceID != "symbol")
+       throw Components.Exception("aInstanceID must be a Symbol()",
+                                  Cr.NS_ERROR_INVALID_ARG);
+
+     for (let [id, val] of this.activeAddons) {
+       if (aInstanceID == val.instanceID) {
+         if (val.safeWrapper) {
+           return Promise.resolve(val.safeWrapper);
+         }
+
+         return new Promise(resolve => {
+           this.getAddonByID(id, function(addon) {
+             val.safeWrapper = new PrivateWrapper(addon);
+             resolve(val.safeWrapper);
+           });
+         });
+       }
+     }
+
+     return Promise.resolve(null);
+   },
+
+  /**
+   * Removes an AddonInstall from the list of active installs.
+   *
+   * @param  install
+   *         The AddonInstall to remove
+   */
+  removeActiveInstall: function(aInstall) {
+    this.installs.delete(aInstall);
+  },
+
+  /**
+   * Called to get an Addon with a particular ID.
+   *
+   * @param  aId
+   *         The ID of the add-on to retrieve
+   * @param  aCallback
+   *         A callback to pass the Addon to
+   */
+  getAddonByID: function(aId, aCallback) {
+    XPIDatabase.getVisibleAddonForID (aId, function(aAddon) {
+      aCallback(aAddon ? aAddon.wrapper : null);
+    });
+  },
+
+  /**
+   * Called to get Addons of a particular type.
+   *
+   * @param  aTypes
+   *         An array of types to fetch. Can be null to get all types.
+   * @param  aCallback
+   *         A callback to pass an array of Addons to
+   */
+  getAddonsByTypes: function(aTypes, aCallback) {
+    let typesToGet = getAllAliasesForTypes(aTypes);
+
+    XPIDatabase.getVisibleAddons(typesToGet, function(aAddons) {
+      aCallback(aAddons.map(a => a.wrapper));
+    });
+  },
+
+  /**
+   * Obtain an Addon having the specified Sync GUID.
+   *
+   * @param  aGUID
+   *         String GUID of add-on to retrieve
+   * @param  aCallback
+   *         A callback to pass the Addon to. Receives null if not found.
+   */
+  getAddonBySyncGUID: function(aGUID, aCallback) {
+    XPIDatabase.getAddonBySyncGUID(aGUID, function(aAddon) {
+      aCallback(aAddon ? aAddon.wrapper : null);
+    });
+  },
+
+  /**
+   * Called to get Addons that have pending operations.
+   *
+   * @param  aTypes
+   *         An array of types to fetch. Can be null to get all types
+   * @param  aCallback
+   *         A callback to pass an array of Addons to
+   */
+  getAddonsWithOperationsByTypes: function(aTypes, aCallback) {
+    let typesToGet = getAllAliasesForTypes(aTypes);
+
+    XPIDatabase.getVisibleAddonsWithPendingOperations(typesToGet, function(aAddons) {
+      let results = aAddons.map(a => a.wrapper);
+      for (let install of XPIProvider.installs) {
+        if (install.state == AddonManager.STATE_INSTALLED &&
+            !(install.addon.inDatabase))
+          results.push(install.addon.wrapper);
+      }
+      aCallback(results);
+    });
+  },
+
+  /**
+   * Called to get the current AddonInstalls, optionally limiting to a list of
+   * types.
+   *
+   * @param  aTypes
+   *         An array of types or null to get all types
+   * @param  aCallback
+   *         A callback to pass the array of AddonInstalls to
+   */
+  getInstallsByTypes: function(aTypes, aCallback) {
+    let results = [...this.installs];
+    if (aTypes) {
+      results = results.filter(install => {
+        return aTypes.includes(getExternalType(install.type));
+      });
+    }
+
+    aCallback(results.map(install => install.wrapper));
+  },
+
+  /**
+   * Synchronously map a URI to the corresponding Addon ID.
+   *
+   * Mappable URIs are limited to in-application resources belonging to the
+   * add-on, such as Javascript compartments, XUL windows, XBL bindings, etc.
+   * but do not include URIs from meta data, such as the add-on homepage.
+   *
+   * @param  aURI
+   *         nsIURI to map or null
+   * @return string containing the Addon ID
+   * @see    AddonManager.mapURIToAddonID
+   * @see    amIAddonManager.mapURIToAddonID
+   */
+  mapURIToAddonID: function(aURI) {
+    // Returns `null` instead of empty string if the URI can't be mapped.
+    return AddonPathService.mapURIToAddonId(aURI) || null;
+  },
+
+  /**
+   * Called when a new add-on has been enabled when only one add-on of that type
+   * can be enabled.
+   *
+   * @param  aId
+   *         The ID of the newly enabled add-on
+   * @param  aType
+   *         The type of the newly enabled add-on
+   * @param  aPendingRestart
+   *         true if the newly enabled add-on will only become enabled after a
+   *         restart
+   */
+  addonChanged: function(aId, aType, aPendingRestart) {
+    // We only care about themes in this provider
+    if (aType != "theme")
+      return;
+
+    if (!aId) {
+      // Fallback to the default theme when no theme was enabled
+      this.enableDefaultTheme();
+      return;
+    }
+
+    // Look for the previously enabled theme and find the internalName of the
+    // currently selected theme
+    let previousTheme = null;
+    let newSkin = this.defaultSkin;
+    let addons = XPIDatabase.getAddonsByType("theme");
+    for (let theme of addons) {
+      if (!theme.visible)
+        return;
+      if (theme.id == aId)
+        newSkin = theme.internalName;
+      else if (theme.userDisabled == false && !theme.pendingUninstall)
+        previousTheme = theme;
+    }
+
+    if (aPendingRestart) {
+      Services.prefs.setBoolPref(PREF_DSS_SWITCHPENDING, true);
+      Services.prefs.setCharPref(PREF_DSS_SKIN_TO_SELECT, newSkin);
+    }
+    else if (newSkin == this.currentSkin) {
+      try {
+        Services.prefs.clearUserPref(PREF_DSS_SWITCHPENDING);
+      }
+      catch (e) { }
+      try {
+        Services.prefs.clearUserPref(PREF_DSS_SKIN_TO_SELECT);
+      }
+      catch (e) { }
+    }
+    else {
+      Services.prefs.setCharPref(PREF_GENERAL_SKINS_SELECTEDSKIN, newSkin);
+      this.currentSkin = newSkin;
+    }
+    this.selectedSkin = newSkin;
+
+    // Flush the preferences to disk so they don't get out of sync with the
+    // database
+    Services.prefs.savePrefFile(null);
+
+    // Mark the previous theme as disabled. This won't cause recursion since
+    // only enabled calls notifyAddonChanged.
+    if (previousTheme)
+      this.updateAddonDisabledState(previousTheme, true);
+  },
+
+  /**
+   * Update the appDisabled property for all add-ons.
+   */
+  updateAddonAppDisabledStates: function() {
+    let addons = XPIDatabase.getAddons();
+    for (let addon of addons) {
+      this.updateAddonDisabledState(addon);
+    }
+  },
+
+  /**
+   * Update the repositoryAddon property for all add-ons.
+   *
+   * @param  aCallback
+   *         Function to call when operation is complete.
+   */
+  updateAddonRepositoryData: function(aCallback) {
+    XPIDatabase.getVisibleAddons(null, aAddons => {
+      let pending = aAddons.length;
+      logger.debug("updateAddonRepositoryData found " + pending + " visible add-ons");
+      if (pending == 0) {
+        aCallback();
+        return;
+      }
+
+      function notifyComplete() {
+        if (--pending == 0)
+          aCallback();
+      }
+
+      for (let addon of aAddons) {
+        AddonRepository.getCachedAddonByID(addon.id, aRepoAddon => {
+          if (aRepoAddon) {
+            logger.debug("updateAddonRepositoryData got info for " + addon.id);
+            addon._repositoryAddon = aRepoAddon;
+            addon.compatibilityOverrides = aRepoAddon.compatibilityOverrides;
+            this.updateAddonDisabledState(addon);
+          }
+
+          notifyComplete();
+        });
+      }
+    });
+  },
+
+  /**
+   * When the previously selected theme is removed this method will be called
+   * to enable the default theme.
+   */
+  enableDefaultTheme: function() {
+    logger.debug("Activating default theme");
+    let addon = XPIDatabase.getVisibleAddonForInternalName(this.defaultSkin);
+    if (addon) {
+      if (addon.userDisabled) {
+        this.updateAddonDisabledState(addon, false);
+      }
+      else if (!this.extensionsActive) {
+        // During startup we may end up trying to enable the default theme when
+        // the database thinks it is already enabled (see f.e. bug 638847). In
+        // this case just force the theme preferences to be correct
+        Services.prefs.setCharPref(PREF_GENERAL_SKINS_SELECTEDSKIN,
+                                   addon.internalName);
+        this.currentSkin = this.selectedSkin = addon.internalName;
+        Preferences.reset(PREF_DSS_SKIN_TO_SELECT);
+        Preferences.reset(PREF_DSS_SWITCHPENDING);
+      }
+      else {
+        logger.warn("Attempting to activate an already active default theme");
+      }
+    }
+    else {
+      logger.warn("Unable to activate the default theme");
+    }
+  },
+
+  onDebugConnectionChange: function(aEvent, aWhat, aConnection) {
+    if (aWhat != "opened")
+      return;
+
+    for (let [id, val] of this.activeAddons) {
+      aConnection.setAddonOptions(
+        id, { global: val.debugGlobal || val.bootstrapScope });
+    }
+  },
+
+  /**
+   * Notified when a preference we're interested in has changed.
+   *
+   * @see nsIObserver
+   */
+  observe: function(aSubject, aTopic, aData) {
+    if (aTopic == NOTIFICATION_FLUSH_PERMISSIONS) {
+      if (!aData || aData == XPI_PERMISSION) {
+        this.importPermissions();
+      }
+      return;
+    }
+    else if (aTopic == NOTIFICATION_TOOLBOXPROCESS_LOADED) {
+      Services.obs.removeObserver(this, NOTIFICATION_TOOLBOXPROCESS_LOADED, false);
+      this._toolboxProcessLoaded = true;
+      BrowserToolboxProcess.on("connectionchange",
+                               this.onDebugConnectionChange.bind(this));
+    }
+
+    if (aTopic == "nsPref:changed") {
+      switch (aData) {
+      case PREF_EM_MIN_COMPAT_APP_VERSION:
+        this.minCompatibleAppVersion = Preferences.get(PREF_EM_MIN_COMPAT_APP_VERSION,
+                                                       null);
+        this.updateAddonAppDisabledStates();
+        break;
+      case PREF_EM_MIN_COMPAT_PLATFORM_VERSION:
+        this.minCompatiblePlatformVersion = Preferences.get(PREF_EM_MIN_COMPAT_PLATFORM_VERSION,
+                                                            null);
+        this.updateAddonAppDisabledStates();
+        break;
+      case PREF_XPI_SIGNATURES_REQUIRED:
+        this.updateAddonAppDisabledStates();
+        break;
+
+      case PREF_E10S_ADDON_BLOCKLIST:
+      case PREF_E10S_ADDON_POLICY:
+        XPIDatabase.updateAddonsBlockingE10s();
+        break;
+      }
+    }
+  },
+
+  /**
+   * Determine if an add-on should be blocking e10s if enabled.
+   *
+   * @param  aAddon
+   *         The add-on to test
+   * @return true if enabling the add-on should block e10s
+   */
+  isBlockingE10s: function(aAddon) {
+    if (aAddon.type != "extension" &&
+        aAddon.type != "webextension" &&
+        aAddon.type != "theme")
+      return false;
+
+    // The hotfix is exempt
+    let hotfixID = Preferences.get(PREF_EM_HOTFIX_ID, undefined);
+    if (hotfixID && hotfixID == aAddon.id)
+      return false;
+
+    // The default theme is exempt
+    if (aAddon.type == "theme" &&
+        aAddon.internalName == XPIProvider.defaultSkin)
+      return false;
+
+    // System add-ons are exempt
+    let locName = aAddon._installLocation ? aAddon._installLocation.name
+                                          : undefined;
+    if (locName == KEY_APP_SYSTEM_DEFAULTS ||
+        locName == KEY_APP_SYSTEM_ADDONS)
+      return false;
+
+    if (isAddonPartOfE10SRollout(aAddon)) {
+      Preferences.set(PREF_E10S_HAS_NONEXEMPT_ADDON, true);
+      return false;
+    }
+
+    logger.debug("Add-on " + aAddon.id + " blocks e10s rollout.");
+    return true;
+  },
+
+  /**
+   * In some cases having add-ons active blocks e10s but turning off e10s
+   * requires a restart so some add-ons that are normally restartless will
+   * require a restart to install or enable.
+   *
+   * @param  aAddon
+   *         The add-on to test
+   * @return true if enabling the add-on requires a restart
+   */
+  e10sBlocksEnabling: function(aAddon) {
+    // If the preference isn't set then don't block anything
+    if (!Preferences.get(PREF_E10S_BLOCK_ENABLE, false))
+      return false;
+
+    // If e10s isn't active then don't block anything
+    if (!Services.appinfo.browserTabsRemoteAutostart)
+      return false;
+
+    return this.isBlockingE10s(aAddon);
+  },
+
+  /**
+   * Tests whether enabling an add-on will require a restart.
+   *
+   * @param  aAddon
+   *         The add-on to test
+   * @return true if the operation requires a restart
+   */
+  enableRequiresRestart: function(aAddon) {
+    // If the platform couldn't have activated extensions then we can make
+    // changes without any restart.
+    if (!this.extensionsActive)
+      return false;
+
+    // If the application is in safe mode then any change can be made without
+    // restarting
+    if (Services.appinfo.inSafeMode)
+      return false;
+
+    // Anything that is active is already enabled
+    if (aAddon.active)
+      return false;
+
+    if (aAddon.type == "theme") {
+      // If dynamic theme switching is enabled then switching themes does not
+      // require a restart
+      if (Preferences.get(PREF_EM_DSS_ENABLED))
+        return false;
+
+      // If the theme is already the theme in use then no restart is necessary.
+      // This covers the case where the default theme is in use but a
+      // lightweight theme is considered active.
+      return aAddon.internalName != this.currentSkin;
+    }
+
+    if (this.e10sBlocksEnabling(aAddon))
+      return true;
+
+    return !aAddon.bootstrap;
+  },
+
+  /**
+   * Tests whether disabling an add-on will require a restart.
+   *
+   * @param  aAddon
+   *         The add-on to test
+   * @return true if the operation requires a restart
+   */
+  disableRequiresRestart: function(aAddon) {
+    // If the platform couldn't have activated up extensions then we can make
+    // changes without any restart.
+    if (!this.extensionsActive)
+      return false;
+
+    // If the application is in safe mode then any change can be made without
+    // restarting
+    if (Services.appinfo.inSafeMode)
+      return false;
+
+    // Anything that isn't active is already disabled
+    if (!aAddon.active)
+      return false;
+
+    if (aAddon.type == "theme") {
+      // If dynamic theme switching is enabled then switching themes does not
+      // require a restart
+      if (Preferences.get(PREF_EM_DSS_ENABLED))
+        return false;
+
+      // Non-default themes always require a restart to disable since it will
+      // be switching from one theme to another or to the default theme and a
+      // lightweight theme.
+      if (aAddon.internalName != this.defaultSkin)
+        return true;
+
+      // The default theme requires a restart to disable if we are in the
+      // process of switching to a different theme. Note that this makes the
+      // disabled flag of operationsRequiringRestart incorrect for the default
+      // theme (it will be false most of the time). Bug 520124 would be required
+      // to fix it. For the UI this isn't a problem since we never try to
+      // disable or uninstall the default theme.
+      return this.selectedSkin != this.currentSkin;
+    }
+
+    return !aAddon.bootstrap;
+  },
+
+  /**
+   * Tests whether installing an add-on will require a restart.
+   *
+   * @param  aAddon
+   *         The add-on to test
+   * @return true if the operation requires a restart
+   */
+  installRequiresRestart: function(aAddon) {
+    // If the platform couldn't have activated up extensions then we can make
+    // changes without any restart.
+    if (!this.extensionsActive)
+      return false;
+
+    // If the application is in safe mode then any change can be made without
+    // restarting
+    if (Services.appinfo.inSafeMode)
+      return false;
+
+    // Add-ons that are already installed don't require a restart to install.
+    // This wouldn't normally be called for an already installed add-on (except
+    // for forming the operationsRequiringRestart flags) so is really here as
+    // a safety measure.
+    if (aAddon.inDatabase)
+      return false;
+
+    // If we have an AddonInstall for this add-on then we can see if there is
+    // an existing installed add-on with the same ID
+    if ("_install" in aAddon && aAddon._install) {
+      // If there is an existing installed add-on and uninstalling it would
+      // require a restart then installing the update will also require a
+      // restart
+      let existingAddon = aAddon._install.existingAddon;
+      if (existingAddon && this.uninstallRequiresRestart(existingAddon))
+        return true;
+    }
+
+    // If the add-on is not going to be active after installation then it
+    // doesn't require a restart to install.
+    if (aAddon.disabled)
+      return false;
+
+    if (this.e10sBlocksEnabling(aAddon))
+      return true;
+
+    // Themes will require a restart (even if dynamic switching is enabled due
+    // to some caching issues) and non-bootstrapped add-ons will require a
+    // restart
+    return aAddon.type == "theme" || !aAddon.bootstrap;
+  },
+
+  /**
+   * Tests whether uninstalling an add-on will require a restart.
+   *
+   * @param  aAddon
+   *         The add-on to test
+   * @return true if the operation requires a restart
+   */
+  uninstallRequiresRestart: function(aAddon) {
+    // If the platform couldn't have activated up extensions then we can make
+    // changes without any restart.
+    if (!this.extensionsActive)
+      return false;
+
+    // If the application is in safe mode then any change can be made without
+    // restarting
+    if (Services.appinfo.inSafeMode)
+      return false;
+
+    // If the add-on can be disabled without a restart then it can also be
+    // uninstalled without a restart
+    return this.disableRequiresRestart(aAddon);
+  },
+
+  /**
+   * Loads a bootstrapped add-on's bootstrap.js into a sandbox and the reason
+   * values as constants in the scope. This will also add information about the
+   * add-on to the bootstrappedAddons dictionary and notify the crash reporter
+   * that new add-ons have been loaded.
+   *
+   * @param  aId
+   *         The add-on's ID
+   * @param  aFile
+   *         The nsIFile for the add-on
+   * @param  aVersion
+   *         The add-on's version
+   * @param  aType
+   *         The type for the add-on
+   * @param  aMultiprocessCompatible
+   *         Boolean indicating whether the add-on is compatible with electrolysis.
+   * @param  aRunInSafeMode
+   *         Boolean indicating whether the add-on can run in safe mode.
+   * @param  aDependencies
+   *         An array of add-on IDs on which this add-on depends.
+   * @param  hasEmbeddedWebExtension
+   *         Boolean indicating whether the add-on has an embedded webextension.
+   * @return a JavaScript scope
+   */
+  loadBootstrapScope: function(aId, aFile, aVersion, aType,
+                               aMultiprocessCompatible, aRunInSafeMode,
+                               aDependencies, hasEmbeddedWebExtension) {
+    // Mark the add-on as active for the crash reporter before loading
+    this.bootstrappedAddons[aId] = {
+      version: aVersion,
+      type: aType,
+      descriptor: aFile.persistentDescriptor,
+      multiprocessCompatible: aMultiprocessCompatible,
+      runInSafeMode: aRunInSafeMode,
+      dependencies: aDependencies,
+      hasEmbeddedWebExtension,
+    };
+    this.persistBootstrappedAddons();
+    this.addAddonsToCrashReporter();
+
+    this.activeAddons.set(aId, {
+      debugGlobal: null,
+      safeWrapper: null,
+      bootstrapScope: null,
+      // a Symbol passed to this add-on, which it can use to identify itself
+      instanceID: Symbol(aId),
+    });
+    let activeAddon = this.activeAddons.get(aId);
+
+    // Locales only contain chrome and can't have bootstrap scripts
+    if (aType == "locale") {
+      return;
+    }
+
+    logger.debug("Loading bootstrap scope from " + aFile.path);
+
+    let principal = Cc["@mozilla.org/systemprincipal;1"].
+                    createInstance(Ci.nsIPrincipal);
+    if (!aMultiprocessCompatible && Preferences.get(PREF_INTERPOSITION_ENABLED, false)) {
+      let interposition = Cc["@mozilla.org/addons/multiprocess-shims;1"].
+        getService(Ci.nsIAddonInterposition);
+      Cu.setAddonInterposition(aId, interposition);
+      Cu.allowCPOWsInAddon(aId, true);
+    }
+
+    if (!aFile.exists()) {
+      activeAddon.bootstrapScope =
+        new Cu.Sandbox(principal, { sandboxName: aFile.path,
+                                    wantGlobalProperties: ["indexedDB"],
+                                    addonId: aId,
+                                    metadata: { addonID: aId } });
+      logger.error("Attempted to load bootstrap scope from missing directory " + aFile.path);
+      return;
+    }
+
+    let uri = getURIForResourceInFile(aFile, "bootstrap.js").spec;
+    if (aType == "dictionary")
+      uri = "resource://gre/modules/addons/SpellCheckDictionaryBootstrap.js"
+    else if (aType == "webextension")
+      uri = "resource://gre/modules/addons/WebExtensionBootstrap.js"
+    else if (aType == "apiextension")
+      uri = "resource://gre/modules/addons/APIExtensionBootstrap.js"
+
+    activeAddon.bootstrapScope =
+      new Cu.Sandbox(principal, { sandboxName: uri,
+                                  wantGlobalProperties: ["indexedDB"],
+                                  addonId: aId,
+                                  metadata: { addonID: aId, URI: uri } });
+
+    let loader = Cc["@mozilla.org/moz/jssubscript-loader;1"].
+                 createInstance(Ci.mozIJSSubScriptLoader);
+
+    try {
+      // Copy the reason values from the global object into the bootstrap scope.
+      for (let name in BOOTSTRAP_REASONS)
+        activeAddon.bootstrapScope[name] = BOOTSTRAP_REASONS[name];
+
+      // Add other stuff that extensions want.
+      const features = [ "Worker", "ChromeWorker" ];
+
+      for (let feature of features)
+        activeAddon.bootstrapScope[feature] = gGlobalScope[feature];
+
+      // Define a console for the add-on
+      activeAddon.bootstrapScope["console"] = new ConsoleAPI(
+        { consoleID: "addon/" + aId });
+
+      // As we don't want our caller to control the JS version used for the
+      // bootstrap file, we run loadSubScript within the context of the
+      // sandbox with the latest JS version set explicitly.
+      activeAddon.bootstrapScope.__SCRIPT_URI_SPEC__ = uri;
+      Components.utils.evalInSandbox(
+        "Components.classes['@mozilla.org/moz/jssubscript-loader;1'] \
+                   .createInstance(Components.interfaces.mozIJSSubScriptLoader) \
+                   .loadSubScript(__SCRIPT_URI_SPEC__);",
+                   activeAddon.bootstrapScope, "ECMAv5");
+    }
+    catch (e) {
+      logger.warn("Error loading bootstrap.js for " + aId, e);
+    }
+
+    // Only access BrowserToolboxProcess if ToolboxProcess.jsm has been
+    // initialized as otherwise, when it will be initialized, all addons'
+    // globals will be added anyways
+    if (this._toolboxProcessLoaded) {
+      BrowserToolboxProcess.setAddonOptions(aId,
+        { global: activeAddon.bootstrapScope });
+    }
+  },
+
+  /**
+   * Unloads a bootstrap scope by dropping all references to it and then
+   * updating the list of active add-ons with the crash reporter.
+   *
+   * @param  aId
+   *         The add-on's ID
+   */
+  unloadBootstrapScope: function(aId) {
+    // In case the add-on was not multiprocess-compatible, deregister
+    // any interpositions for it.
+    Cu.setAddonInterposition(aId, null);
+    Cu.allowCPOWsInAddon(aId, false);
+
+    this.activeAddons.delete(aId);
+    delete this.bootstrappedAddons[aId];
+    this.persistBootstrappedAddons();
+    this.addAddonsToCrashReporter();
+
+    // Only access BrowserToolboxProcess if ToolboxProcess.jsm has been
+    // initialized as otherwise, there won't be any addon globals added to it
+    if (this._toolboxProcessLoaded) {
+      BrowserToolboxProcess.setAddonOptions(aId, { global: null });
+    }
+  },
+
+  /**
+   * Calls a bootstrap method for an add-on.
+   *
+   * @param  aAddon
+   *         An object representing the add-on, with `id`, `type` and `version`
+   * @param  aFile
+   *         The nsIFile for the add-on
+   * @param  aMethod
+   *         The name of the bootstrap method to call
+   * @param  aReason
+   *         The reason flag to pass to the bootstrap's startup method
+   * @param  aExtraParams
+   *         An object of additional key/value pairs to pass to the method in
+   *         the params argument
+   */
+  callBootstrapMethod: function(aAddon, aFile, aMethod, aReason, aExtraParams) {
+    if (!aAddon.id || !aAddon.version || !aAddon.type) {
+      throw new Error("aAddon must include an id, version, and type");
+    }
+
+    // Only run in safe mode if allowed to
+    let runInSafeMode = "runInSafeMode" in aAddon ? aAddon.runInSafeMode : canRunInSafeMode(aAddon);
+    if (Services.appinfo.inSafeMode && !runInSafeMode)
+      return;
+
+    let timeStart = new Date();
+    if (CHROME_TYPES.has(aAddon.type) && aMethod == "startup") {
+      logger.debug("Registering manifest for " + aFile.path);
+      Components.manager.addBootstrappedManifestLocation(aFile);
+    }
+
+    try {
+      // Load the scope if it hasn't already been loaded
+      let activeAddon = this.activeAddons.get(aAddon.id);
+      if (!activeAddon) {
+        this.loadBootstrapScope(aAddon.id, aFile, aAddon.version, aAddon.type,
+                                aAddon.multiprocessCompatible || false,
+                                runInSafeMode, aAddon.dependencies,
+                                aAddon.hasEmbeddedWebExtension || false);
+        activeAddon = this.activeAddons.get(aAddon.id);
+      }
+
+      if (aMethod == "startup" || aMethod == "shutdown") {
+        if (!aExtraParams) {
+          aExtraParams = {};
+        }
+        aExtraParams["instanceID"] = this.activeAddons.get(aAddon.id).instanceID;
+      }
+
+      // Nothing to call for locales
+      if (aAddon.type == "locale")
+        return;
+
+      let method = undefined;
+      try {
+        method = Components.utils.evalInSandbox(`${aMethod};`,
+          activeAddon.bootstrapScope, "ECMAv5");
+      }
+      catch (e) {
+        // An exception will be caught if the expected method is not defined.
+        // That will be logged below.
+      }
+
+      if (!method) {
+        logger.warn("Add-on " + aAddon.id + " is missing bootstrap method " + aMethod);
+        return;
+      }
+
+      // Extensions are automatically deinitialized in the correct order at shutdown.
+      if (aMethod == "shutdown" && aReason != BOOTSTRAP_REASONS.APP_SHUTDOWN) {
+        activeAddon.disable = true;
+        for (let addon of this.getDependentAddons(aAddon)) {
+          if (addon.active)
+            this.updateAddonDisabledState(addon);
+        }
+      }
+
+      let params = {
+        id: aAddon.id,
+        version: aAddon.version,
+        installPath: aFile.clone(),
+        resourceURI: getURIForResourceInFile(aFile, "")
+      };
+
+      if (aExtraParams) {
+        for (let key in aExtraParams) {
+          params[key] = aExtraParams[key];
+        }
+      }
+
+      if (aAddon.hasEmbeddedWebExtension) {
+        if (aMethod == "startup") {
+          const webExtension = LegacyExtensionsUtils.getEmbeddedExtensionFor(params);
+          params.webExtension = {
+            startup: () => webExtension.startup(),
+          };
+        } else if (aMethod == "shutdown") {
+          LegacyExtensionsUtils.getEmbeddedExtensionFor(params).shutdown();
+        }
+      }
+
+      logger.debug("Calling bootstrap method " + aMethod + " on " + aAddon.id + " version " +
+                   aAddon.version);
+      try {
+        method(params, aReason);
+      }
+      catch (e) {
+        logger.warn("Exception running bootstrap method " + aMethod + " on " + aAddon.id, e);
+      }
+    }
+    finally {
+      // Extensions are automatically initialized in the correct order at startup.
+      if (aMethod == "startup" && aReason != BOOTSTRAP_REASONS.APP_STARTUP) {
+        for (let addon of this.getDependentAddons(aAddon))
+          this.updateAddonDisabledState(addon);
+      }
+
+      if (CHROME_TYPES.has(aAddon.type) && aMethod == "shutdown" && aReason != BOOTSTRAP_REASONS.APP_SHUTDOWN) {
+        logger.debug("Removing manifest for " + aFile.path);
+        Components.manager.removeBootstrappedManifestLocation(aFile);
+
+        let manifest = getURIForResourceInFile(aFile, "chrome.manifest");
+        for (let line of ChromeManifestParser.parseSync(manifest)) {
+          if (line.type == "resource") {
+            ResProtocolHandler.setSubstitution(line.args[0], null);
+          }
+        }
+      }
+      this.setTelemetry(aAddon.id, aMethod + "_MS", new Date() - timeStart);
+    }
+  },
+
+  /**
+   * Updates the disabled state for an add-on. Its appDisabled property will be
+   * calculated and if the add-on is changed the database will be saved and
+   * appropriate notifications will be sent out to the registered AddonListeners.
+   *
+   * @param  aAddon
+   *         The DBAddonInternal to update
+   * @param  aUserDisabled
+   *         Value for the userDisabled property. If undefined the value will
+   *         not change
+   * @param  aSoftDisabled
+   *         Value for the softDisabled property. If undefined the value will
+   *         not change. If true this will force userDisabled to be true
+   * @return a tri-state indicating the action taken for the add-on:
+   *           - undefined: The add-on did not change state
+   *           - true: The add-on because disabled
+   *           - false: The add-on became enabled
+   * @throws if addon is not a DBAddonInternal
+   */
+  updateAddonDisabledState: function(aAddon, aUserDisabled, aSoftDisabled) {
+    if (!(aAddon.inDatabase))
+      throw new Error("Can only update addon states for installed addons.");
+    if (aUserDisabled !== undefined && aSoftDisabled !== undefined) {
+      throw new Error("Cannot change userDisabled and softDisabled at the " +
+                      "same time");
+    }
+
+    if (aUserDisabled === undefined) {
+      aUserDisabled = aAddon.userDisabled;
+    }
+    else if (!aUserDisabled) {
+      // If enabling the add-on then remove softDisabled
+      aSoftDisabled = false;
+    }
+
+    // If not changing softDisabled or the add-on is already userDisabled then
+    // use the existing value for softDisabled
+    if (aSoftDisabled === undefined || aUserDisabled)
+      aSoftDisabled = aAddon.softDisabled;
+
+    let appDisabled = !isUsableAddon(aAddon);
+    // No change means nothing to do here
+    if (aAddon.userDisabled == aUserDisabled &&
+        aAddon.appDisabled == appDisabled &&
+        aAddon.softDisabled == aSoftDisabled)
+      return undefined;
+
+    let wasDisabled = aAddon.disabled;
+    let isDisabled = aUserDisabled || aSoftDisabled || appDisabled;
+
+    // If appDisabled changes but addon.disabled doesn't,
+    // no onDisabling/onEnabling is sent - so send a onPropertyChanged.
+    let appDisabledChanged = aAddon.appDisabled != appDisabled;
+
+    // Update the properties in the database.
+    XPIDatabase.setAddonProperties(aAddon, {
+      userDisabled: aUserDisabled,
+      appDisabled: appDisabled,
+      softDisabled: aSoftDisabled
+    });
+
+    let wrapper = aAddon.wrapper;
+
+    if (appDisabledChanged) {
+      AddonManagerPrivate.callAddonListeners("onPropertyChanged",
+                                             wrapper,
+                                             ["appDisabled"]);
+    }
+
+    // If the add-on is not visible or the add-on is not changing state then
+    // there is no need to do anything else
+    if (!aAddon.visible || (wasDisabled == isDisabled))
+      return undefined;
+
+    // Flag that active states in the database need to be updated on shutdown
+    Services.prefs.setBoolPref(PREF_PENDING_OPERATIONS, true);
+
+    // Have we just gone back to the current state?
+    if (isDisabled != aAddon.active) {
+      AddonManagerPrivate.callAddonListeners("onOperationCancelled", wrapper);
+    }
+    else {
+      if (isDisabled) {
+        var needsRestart = this.disableRequiresRestart(aAddon);
+        AddonManagerPrivate.callAddonListeners("onDisabling", wrapper,
+                                               needsRestart);
+      }
+      else {
+        needsRestart = this.enableRequiresRestart(aAddon);
+        AddonManagerPrivate.callAddonListeners("onEnabling", wrapper,
+                                               needsRestart);
+      }
+
+      if (!needsRestart) {
+        XPIDatabase.updateAddonActive(aAddon, !isDisabled);
+
+        if (isDisabled) {
+          if (aAddon.bootstrap) {
+            this.callBootstrapMethod(aAddon, aAddon._sourceBundle, "shutdown",
+                                     BOOTSTRAP_REASONS.ADDON_DISABLE);
+            this.unloadBootstrapScope(aAddon.id);
+          }
+          AddonManagerPrivate.callAddonListeners("onDisabled", wrapper);
+        }
+        else {
+          if (aAddon.bootstrap) {
+            this.callBootstrapMethod(aAddon, aAddon._sourceBundle, "startup",
+                                     BOOTSTRAP_REASONS.ADDON_ENABLE);
+          }
+          AddonManagerPrivate.callAddonListeners("onEnabled", wrapper);
+        }
+      }
+      else if (aAddon.bootstrap) {
+        // Something blocked the restartless add-on from enabling or disabling
+        // make sure it happens on the next startup
+        if (isDisabled) {
+          this.bootstrappedAddons[aAddon.id].disable = true;
+        }
+        else {
+          this.bootstrappedAddons[aAddon.id] = {
+            version: aAddon.version,
+            type: aAddon.type,
+            descriptor: aAddon._sourceBundle.persistentDescriptor,
+            multiprocessCompatible: aAddon.multiprocessCompatible,
+            runInSafeMode: canRunInSafeMode(aAddon),
+            dependencies: aAddon.dependencies,
+            hasEmbeddedWebExtension: aAddon.hasEmbeddedWebExtension,
+          };
+          this.persistBootstrappedAddons();
+        }
+      }
+    }
+
+    // Sync with XPIStates.
+    let xpiState = XPIStates.getAddon(aAddon.location, aAddon.id);
+    if (xpiState) {
+      xpiState.syncWithDB(aAddon);
+      XPIStates.save();
+    } else {
+      // There should always be an xpiState
+      logger.warn("No XPIState for ${id} in ${location}", aAddon);
+    }
+
+    // Notify any other providers that a new theme has been enabled
+    if (aAddon.type == "theme" && !isDisabled)
+      AddonManagerPrivate.notifyAddonChanged(aAddon.id, aAddon.type, needsRestart);
+
+    return isDisabled;
+  },
+
+  /**
+   * Uninstalls an add-on, immediately if possible or marks it as pending
+   * uninstall if not.
+   *
+   * @param  aAddon
+   *         The DBAddonInternal to uninstall
+   * @param  aForcePending
+   *         Force this addon into the pending uninstall state, even if
+   *         it isn't marked as requiring a restart (used e.g. while the
+   *         add-on manager is open and offering an "undo" button)
+   * @throws if the addon cannot be uninstalled because it is in an install
+   *         location that does not allow it
+   */
+  uninstallAddon: function(aAddon, aForcePending) {
+    if (!(aAddon.inDatabase))
+      throw new Error("Cannot uninstall addon " + aAddon.id + " because it is not installed");
+
+    if (aAddon._installLocation.locked)
+      throw new Error("Cannot uninstall addon " + aAddon.id
+          + " from locked install location " + aAddon._installLocation.name);
+
+    // Inactive add-ons don't require a restart to uninstall
+    let requiresRestart = this.uninstallRequiresRestart(aAddon);
+
+    // if makePending is true, we don't actually apply the uninstall,
+    // we just mark the addon as having a pending uninstall
+    let makePending = aForcePending || requiresRestart;
+
+    if (makePending && aAddon.pendingUninstall)
+      throw new Error("Add-on is already marked to be uninstalled");
+
+    aAddon._hasResourceCache.clear();
+
+    if (aAddon._updateCheck) {
+      logger.debug("Cancel in-progress update check for " + aAddon.id);
+      aAddon._updateCheck.cancel();
+    }
+
+    let wasPending = aAddon.pendingUninstall;
+
+    if (makePending) {
+      // We create an empty directory in the staging directory to indicate
+      // that an uninstall is necessary on next startup. Temporary add-ons are
+      // automatically uninstalled on shutdown anyway so there is no need to
+      // do this for them.
+      if (aAddon._installLocation.name != KEY_APP_TEMPORARY) {
+        let stage = aAddon._installLocation.getStagingDir();
+        stage.append(aAddon.id);
+        if (!stage.exists())
+          stage.create(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+      }
+
+      XPIDatabase.setAddonProperties(aAddon, {
+        pendingUninstall: true
+      });
+      Services.prefs.setBoolPref(PREF_PENDING_OPERATIONS, true);
+      let xpiState = XPIStates.getAddon(aAddon.location, aAddon.id);
+      if (xpiState) {
+        xpiState.enabled = false;
+        XPIStates.save();
+      } else {
+        logger.warn("Can't find XPI state while uninstalling ${id} from ${location}", aAddon);
+      }
+    }
+
+    // If the add-on is not visible then there is no need to notify listeners.
+    if (!aAddon.visible)
+      return;
+
+    let wrapper = aAddon.wrapper;
+
+    // If the add-on wasn't already pending uninstall then notify listeners.
+    if (!wasPending) {
+      // Passing makePending as the requiresRestart parameter is a little
+      // strange as in some cases this operation can complete without a restart
+      // so really this is now saying that the uninstall isn't going to happen
+      // immediately but will happen later.
+      AddonManagerPrivate.callAddonListeners("onUninstalling", wrapper,
+                                             makePending);
+    }
+
+    // Reveal the highest priority add-on with the same ID
+    function revealAddon(aAddon) {
+      XPIDatabase.makeAddonVisible(aAddon);
+
+      let wrappedAddon = aAddon.wrapper;
+      AddonManagerPrivate.callAddonListeners("onInstalling", wrappedAddon, false);
+
+      if (!aAddon.disabled && !XPIProvider.enableRequiresRestart(aAddon)) {
+        XPIDatabase.updateAddonActive(aAddon, true);
+      }
+
+      if (aAddon.bootstrap) {
+        XPIProvider.callBootstrapMethod(aAddon, aAddon._sourceBundle,
+                                        "install", BOOTSTRAP_REASONS.ADDON_INSTALL);
+
+        if (aAddon.active) {
+          XPIProvider.callBootstrapMethod(aAddon, aAddon._sourceBundle,
+                                          "startup", BOOTSTRAP_REASONS.ADDON_INSTALL);
+        }
+        else {
+          XPIProvider.unloadBootstrapScope(aAddon.id);
+        }
+      }
+
+      // We always send onInstalled even if a restart is required to enable
+      // the revealed add-on
+      AddonManagerPrivate.callAddonListeners("onInstalled", wrappedAddon);
+    }
+
+    function findAddonAndReveal(aId) {
+      let [locationName, ] = XPIStates.findAddon(aId);
+      if (locationName) {
+        XPIDatabase.getAddonInLocation(aId, locationName, revealAddon);
+      }
+    }
+
+    if (!makePending) {
+      if (aAddon.bootstrap) {
+        if (aAddon.active) {
+          this.callBootstrapMethod(aAddon, aAddon._sourceBundle, "shutdown",
+                                   BOOTSTRAP_REASONS.ADDON_UNINSTALL);
+        }
+
+        this.callBootstrapMethod(aAddon, aAddon._sourceBundle, "uninstall",
+                                 BOOTSTRAP_REASONS.ADDON_UNINSTALL);
+        this.unloadBootstrapScope(aAddon.id);
+        flushChromeCaches();
+      }
+      aAddon._installLocation.uninstallAddon(aAddon.id);
+      XPIDatabase.removeAddonMetadata(aAddon);
+      XPIStates.removeAddon(aAddon.location, aAddon.id);
+      AddonManagerPrivate.callAddonListeners("onUninstalled", wrapper);
+
+      findAddonAndReveal(aAddon.id);
+    }
+    else if (aAddon.bootstrap && aAddon.active && !this.disableRequiresRestart(aAddon)) {
+      this.callBootstrapMethod(aAddon, aAddon._sourceBundle, "shutdown",
+                               BOOTSTRAP_REASONS.ADDON_UNINSTALL);
+      this.unloadBootstrapScope(aAddon.id);
+      XPIDatabase.updateAddonActive(aAddon, false);
+    }
+
+    // Notify any other providers that a new theme has been enabled
+    if (aAddon.type == "theme" && aAddon.active)
+      AddonManagerPrivate.notifyAddonChanged(null, aAddon.type, requiresRestart);
+  },
+
+  /**
+   * Cancels the pending uninstall of an add-on.
+   *
+   * @param  aAddon
+   *         The DBAddonInternal to cancel uninstall for
+   */
+  cancelUninstallAddon: function(aAddon) {
+    if (!(aAddon.inDatabase))
+      throw new Error("Can only cancel uninstall for installed addons.");
+    if (!aAddon.pendingUninstall)
+      throw new Error("Add-on is not marked to be uninstalled");
+
+    if (aAddon._installLocation.name != KEY_APP_TEMPORARY)
+      aAddon._installLocation.cleanStagingDir([aAddon.id]);
+
+    XPIDatabase.setAddonProperties(aAddon, {
+      pendingUninstall: false
+    });
+
+    if (!aAddon.visible)
+      return;
+
+    Services.prefs.setBoolPref(PREF_PENDING_OPERATIONS, true);
+
+    // TODO hide hidden add-ons (bug 557710)
+    let wrapper = aAddon.wrapper;
+    AddonManagerPrivate.callAddonListeners("onOperationCancelled", wrapper);
+
+    if (aAddon.bootstrap && !aAddon.disabled && !this.enableRequiresRestart(aAddon)) {
+      this.callBootstrapMethod(aAddon, aAddon._sourceBundle, "startup",
+                               BOOTSTRAP_REASONS.ADDON_INSTALL);
+      XPIDatabase.updateAddonActive(aAddon, true);
+    }
+
+    // Notify any other providers that this theme is now enabled again.
+    if (aAddon.type == "theme" && aAddon.active)
+      AddonManagerPrivate.notifyAddonChanged(aAddon.id, aAddon.type, false);
+  }
+};
+
+function getHashStringForCrypto(aCrypto) {
+  // return the two-digit hexadecimal code for a byte
+  let toHexString = charCode => ("0" + charCode.toString(16)).slice(-2);
+
+  // convert the binary hash data to a hex string.
+  let binary = aCrypto.finish(false);
+  let hash = Array.from(binary, c => toHexString(c.charCodeAt(0)))
+  return hash.join("").toLowerCase();
+}
+
+/**
+ * Base class for objects that manage the installation of an addon.
+ * This class isn't instantiated directly, see the derived classes below.
+ */
+class AddonInstall {
+  /**
+   * Instantiates an AddonInstall.
+   *
+   * @param  aInstallLocation
+   *         The install location the add-on will be installed into
+   * @param  aUrl
+   *         The nsIURL to get the add-on from. If this is an nsIFileURL then
+   *         the add-on will not need to be downloaded
+   * @param  aHash
+   *         An optional hash for the add-on
+   * @param  aExistingAddon
+   *         The add-on this install will update if known
+   */
+  constructor(aInstallLocation, aUrl, aHash, aExistingAddon) {
+    this.wrapper = new AddonInstallWrapper(this);
+    this.installLocation = aInstallLocation;
+    this.sourceURI = aUrl;
+
+    if (aHash) {
+      let hashSplit = aHash.toLowerCase().split(":");
+      this.originalHash = {
+        algorithm: hashSplit[0],
+        data: hashSplit[1]
+      };
+    }
+    this.hash = this.originalHash;
+    this.existingAddon = aExistingAddon;
+    this.releaseNotesURI = null;
+
+    this.listeners = [];
+    this.icons = {};
+    this.error = 0;
+
+    this.progress = 0;
+    this.maxProgress = -1;
+
+    // Giving each instance of AddonInstall a reference to the logger.
+    this.logger = logger;
+
+    this.name = null;
+    this.type = null;
+    this.version = null;
+
+    this.file = null;
+    this.ownsTempFile = null;
+    this.certificate = null;
+    this.certName = null;
+
+    this.linkedInstalls = null;
+    this.addon = null;
+    this.state = null;
+
+    XPIProvider.installs.add(this);
+  }
+
+  /**
+   * Starts installation of this add-on from whatever state it is currently at
+   * if possible.
+   *
+   * Note this method is overridden to handle additional state in
+   * the subclassses below.
+   *
+   * @throws if installation cannot proceed from the current state
+   */
+  install() {
+    switch (this.state) {
+    case AddonManager.STATE_DOWNLOADED:
+      this.startInstall();
+      break;
+    case AddonManager.STATE_POSTPONED:
+      logger.debug(`Postponing install of ${this.addon.id}`);
+      break;
+    case AddonManager.STATE_DOWNLOADING:
+    case AddonManager.STATE_CHECKING:
+    case AddonManager.STATE_INSTALLING:
+      // Installation is already running
+      return;
+    default:
+      throw new Error("Cannot start installing from this state");
+    }
+  }
+
+  /**
+   * Cancels installation of this add-on.
+   *
+   * Note this method is overridden to handle additional state in
+   * the subclass DownloadAddonInstall.
+   *
+   * @throws if installation cannot be cancelled from the current state
+   */
+  cancel() {
+    switch (this.state) {
+    case AddonManager.STATE_AVAILABLE:
+    case AddonManager.STATE_DOWNLOADED:
+      logger.debug("Cancelling download of " + this.sourceURI.spec);
+      this.state = AddonManager.STATE_CANCELLED;
+      XPIProvider.removeActiveInstall(this);
+      AddonManagerPrivate.callInstallListeners("onDownloadCancelled",
+                                               this.listeners, this.wrapper);
+      this.removeTemporaryFile();
+      break;
+    case AddonManager.STATE_INSTALLED:
+      logger.debug("Cancelling install of " + this.addon.id);
+      let xpi = this.installLocation.getStagingDir();
+      xpi.append(this.addon.id + ".xpi");
+      flushJarCache(xpi);
+      this.installLocation.cleanStagingDir([this.addon.id, this.addon.id + ".xpi",
+                                            this.addon.id + ".json"]);
+      this.state = AddonManager.STATE_CANCELLED;
+      XPIProvider.removeActiveInstall(this);
+
+      if (this.existingAddon) {
+        delete this.existingAddon.pendingUpgrade;
+        this.existingAddon.pendingUpgrade = null;
+      }
+
+      AddonManagerPrivate.callAddonListeners("onOperationCancelled", this.addon.wrapper);
+
+      AddonManagerPrivate.callInstallListeners("onInstallCancelled",
+                                               this.listeners, this.wrapper);
+      break;
+    case AddonManager.STATE_POSTPONED:
+      logger.debug(`Cancelling postponed install of ${this.addon.id}`);
+      this.state = AddonManager.STATE_CANCELLED;
+      XPIProvider.removeActiveInstall(this);
+      AddonManagerPrivate.callInstallListeners("onInstallCancelled",
+                                               this.listeners, this.wrapper);
+      this.removeTemporaryFile();
+
+      let stagingDir = this.installLocation.getStagingDir();
+      let stagedAddon = stagingDir.clone();
+
+      this.unstageInstall(stagedAddon);
+    default:
+      throw new Error("Cannot cancel install of " + this.sourceURI.spec +
+                      " from this state (" + this.state + ")");
+    }
+  }
+
+  /**
+   * Adds an InstallListener for this instance if the listener is not already
+   * registered.
+   *
+   * @param  aListener
+   *         The InstallListener to add
+   */
+  addListener(aListener) {
+    if (!this.listeners.some(function(i) { return i == aListener; }))
+      this.listeners.push(aListener);
+  }
+
+  /**
+   * Removes an InstallListener for this instance if it is registered.
+   *
+   * @param  aListener
+   *         The InstallListener to remove
+   */
+  removeListener(aListener) {
+    this.listeners = this.listeners.filter(function(i) {
+      return i != aListener;
+    });
+  }
+
+  /**
+   * Removes the temporary file owned by this AddonInstall if there is one.
+   */
+  removeTemporaryFile() {
+    // Only proceed if this AddonInstall owns its XPI file
+    if (!this.ownsTempFile) {
+      this.logger.debug("removeTemporaryFile: " + this.sourceURI.spec + " does not own temp file");
+      return;
+    }
+
+    try {
+      this.logger.debug("removeTemporaryFile: " + this.sourceURI.spec + " removing temp file " +
+          this.file.path);
+      this.file.remove(true);
+      this.ownsTempFile = false;
+    }
+    catch (e) {
+      this.logger.warn("Failed to remove temporary file " + this.file.path + " for addon " +
+          this.sourceURI.spec,
+          e);
+    }
+  }
+
+  /**
+   * Updates the sourceURI and releaseNotesURI values on the Addon being
+   * installed by this AddonInstall instance.
+   */
+  updateAddonURIs() {
+    this.addon.sourceURI = this.sourceURI.spec;
+    if (this.releaseNotesURI)
+      this.addon.releaseNotesURI = this.releaseNotesURI.spec;
+  }
+
+  /**
+   * Fills out linkedInstalls with AddonInstall instances for the other files
+   * in a multi-package XPI.
+   *
+   * @param  aFiles
+   *         An array of { entryName, file } for each remaining file from the
+   *         multi-package XPI.
+   */
+  _createLinkedInstalls(aFiles) {
+    return Task.spawn((function*() {
+      if (aFiles.length == 0)
+        return;
+
+      // Create new AddonInstall instances for every remaining file
+      if (!this.linkedInstalls)
+        this.linkedInstalls = [];
+
+      for (let { entryName, file } of aFiles) {
+        logger.debug("Creating linked install from " + entryName);
+        let install = yield createLocalInstall(file);
+
+        // Make the new install own its temporary file
+        install.ownsTempFile = true;
+
+        this.linkedInstalls.push(install);
+
+        // If one of the internal XPIs was multipackage then move its linked
+        // installs to the outer install
+        if (install.linkedInstalls) {
+          this.linkedInstalls.push(...install.linkedInstalls);
+          install.linkedInstalls = null;
+        }
+
+        install.sourceURI = this.sourceURI;
+        install.releaseNotesURI = this.releaseNotesURI;
+        if (install.state != AddonManager.STATE_DOWNLOAD_FAILED)
+          install.updateAddonURIs();
+      }
+    }).bind(this));
+  }
+
+  /**
+   * Loads add-on manifests from a multi-package XPI file. Each of the
+   * XPI and JAR files contained in the XPI will be extracted. Any that
+   * do not contain valid add-ons will be ignored. The first valid add-on will
+   * be installed by this AddonInstall instance, the rest will have new
+   * AddonInstall instances created for them.
+   *
+   * @param  aZipReader
+   *         An open nsIZipReader for the multi-package XPI's files. This will
+   *         be closed before this method returns.
+   */
+  _loadMultipackageManifests(aZipReader) {
+    return Task.spawn((function*() {
+      let files = [];
+      let entries = aZipReader.findEntries("(*.[Xx][Pp][Ii]|*.[Jj][Aa][Rr])");
+      while (entries.hasMore()) {
+        let entryName = entries.getNext();
+        let file = getTemporaryFile();
+        try {
+          aZipReader.extract(entryName, file);
+          files.push({ entryName, file });
+        }
+        catch (e) {
+          logger.warn("Failed to extract " + entryName + " from multi-package " +
+                      "XPI", e);
+          file.remove(false);
+        }
+      }
+
+      aZipReader.close();
+
+      if (files.length == 0) {
+        return Promise.reject([AddonManager.ERROR_CORRUPT_FILE,
+                               "Multi-package XPI does not contain any packages to install"]);
+      }
+
+      let addon = null;
+
+      // Find the first file that is a valid install and use it for
+      // the add-on that this AddonInstall instance will install.
+      for (let { entryName, file } of files) {
+        this.removeTemporaryFile();
+        try {
+          yield this.loadManifest(file);
+          logger.debug("Base multi-package XPI install came from " + entryName);
+          this.file = file;
+          this.ownsTempFile = true;
+
+          yield this._createLinkedInstalls(files.filter(f => f.file != file));
+          return undefined;
+        }
+        catch (e) {
+          // _createLinkedInstalls will log errors when it tries to process this
+          // file
+        }
+      }
+
+      // No valid add-on was found, delete all the temporary files
+      for (let { file } of files) {
+        try {
+          file.remove(true);
+        } catch (e) {
+          this.logger.warn("Could not remove temp file " + file.path);
+        }
+      }
+
+      return Promise.reject([AddonManager.ERROR_CORRUPT_FILE,
+                             "Multi-package XPI does not contain any valid packages to install"]);
+    }).bind(this));
+  }
+
+  /**
+   * Called after the add-on is a local file and the signature and install
+   * manifest can be read.
+   *
+   * @param  aCallback
+   *         A function to call when the manifest has been loaded
+   * @throws if the add-on does not contain a valid install manifest or the
+   *         XPI is incorrectly signed
+   */
+  loadManifest(file) {
+    return Task.spawn((function*() {
+      let zipreader = Cc["@mozilla.org/libjar/zip-reader;1"].
+          createInstance(Ci.nsIZipReader);
+      try {
+        zipreader.open(file);
+      }
+      catch (e) {
+        zipreader.close();
+        return Promise.reject([AddonManager.ERROR_CORRUPT_FILE, e]);
+      }
+
+      try {
+        // loadManifestFromZipReader performs the certificate verification for us
+        this.addon = yield loadManifestFromZipReader(zipreader, this.installLocation);
+      }
+      catch (e) {
+        zipreader.close();
+        return Promise.reject([AddonManager.ERROR_CORRUPT_FILE, e]);
+      }
+
+      // A multi-package XPI is a container, the add-ons it holds each
+      // have their own id.  Everything else had better have an id here.
+      if (!this.addon.id && this.addon.type != "multipackage") {
+        let err = new Error(`Cannot find id for addon ${file.path}`);
+        return Promise.reject([AddonManager.ERROR_CORRUPT_FILE, err]);
+      }
+
+      if (this.existingAddon) {
+        // Check various conditions related to upgrades
+        if (this.addon.id != this.existingAddon.id) {
+          zipreader.close();
+          return Promise.reject([AddonManager.ERROR_INCORRECT_ID,
+                                 `Refusing to upgrade addon ${this.existingAddon.id} to different ID {this.addon.id}`]);
+        }
+
+        if (this.addon.type == "multipackage") {
+          zipreader.close();
+          return Promise.reject([AddonManager.ERROR_UNEXPECTED_ADDON_TYPE,
+                                 `Refusing to upgrade addon ${this.existingAddon.id} to a multi-package xpi`]);
+        }
+
+        if (this.existingAddon.type == "webextension" && this.addon.type != "webextension") {
+          zipreader.close();
+          return Promise.reject([AddonManager.ERROR_UNEXPECTED_ADDON_TYPE,
+                                 "WebExtensions may not be upated to other extension types"]);
+        }
+      }
+
+      if (mustSign(this.addon.type)) {
+        if (this.addon.signedState <= AddonManager.SIGNEDSTATE_MISSING) {
+          // This add-on isn't properly signed by a signature that chains to the
+          // trusted root.
+          let state = this.addon.signedState;
+          this.addon = null;
+          zipreader.close();
+
+          if (state == AddonManager.SIGNEDSTATE_MISSING)
+            return Promise.reject([AddonManager.ERROR_SIGNEDSTATE_REQUIRED,
+                                   "signature is required but missing"])
+
+          return Promise.reject([AddonManager.ERROR_CORRUPT_FILE,
+                                 "signature verification failed"])
+        }
+      }
+      else if (this.addon.signedState == AddonManager.SIGNEDSTATE_UNKNOWN ||
+               this.addon.signedState == AddonManager.SIGNEDSTATE_NOT_REQUIRED) {
+        // Check object signing certificate, if any
+        let x509 = zipreader.getSigningCert(null);
+        if (x509) {
+          logger.debug("Verifying XPI signature");
+          if (verifyZipSigning(zipreader, x509)) {
+            this.certificate = x509;
+            if (this.certificate.commonName.length > 0) {
+              this.certName = this.certificate.commonName;
+            } else {
+              this.certName = this.certificate.organization;
+            }
+          } else {
+            zipreader.close();
+            return Promise.reject([AddonManager.ERROR_CORRUPT_FILE,
+                                   "XPI is incorrectly signed"]);
+          }
+        }
+      }
+
+      if (this.addon.type == "multipackage")
+        return this._loadMultipackageManifests(zipreader);
+
+      zipreader.close();
+
+      this.updateAddonURIs();
+
+      this.addon._install = this;
+      this.name = this.addon.selectedLocale.name;
+      this.type = this.addon.type;
+      this.version = this.addon.version;
+
+      // Setting the iconURL to something inside the XPI locks the XPI and
+      // makes it impossible to delete on Windows.
+
+      // Try to load from the existing cache first
+      let repoAddon = yield new Promise(resolve => AddonRepository.getCachedAddonByID(this.addon.id, resolve));
+
+      // It wasn't there so try to re-download it
+      if (!repoAddon) {
+        yield new Promise(resolve => AddonRepository.cacheAddons([this.addon.id], resolve));
+        repoAddon = yield new Promise(resolve => AddonRepository.getCachedAddonByID(this.addon.id, resolve));
+      }
+
+      this.addon._repositoryAddon = repoAddon;
+      this.name = this.name || this.addon._repositoryAddon.name;
+      this.addon.compatibilityOverrides = repoAddon ?
+        repoAddon.compatibilityOverrides :
+        null;
+      this.addon.appDisabled = !isUsableAddon(this.addon);
+      return undefined;
+    }).bind(this));
+  }
+
+  // TODO This relies on the assumption that we are always installing into the
+  // highest priority install location so the resulting add-on will be visible
+  // overriding any existing copy in another install location (bug 557710).
+  /**
+   * Installs the add-on into the install location.
+   */
+  startInstall() {
+    this.state = AddonManager.STATE_INSTALLING;
+    if (!AddonManagerPrivate.callInstallListeners("onInstallStarted",
+                                                  this.listeners, this.wrapper)) {
+      this.state = AddonManager.STATE_DOWNLOADED;
+      XPIProvider.removeActiveInstall(this);
+      AddonManagerPrivate.callInstallListeners("onInstallCancelled",
+                                               this.listeners, this.wrapper)
+      return;
+    }
+
+    // Find and cancel any pending installs for the same add-on in the same
+    // install location
+    for (let aInstall of XPIProvider.installs) {
+      if (aInstall.state == AddonManager.STATE_INSTALLED &&
+          aInstall.installLocation == this.installLocation &&
+          aInstall.addon.id == this.addon.id) {
+        logger.debug("Cancelling previous pending install of " + aInstall.addon.id);
+        aInstall.cancel();
+      }
+    }
+
+    let isUpgrade = this.existingAddon &&
+                    this.existingAddon._installLocation == this.installLocation;
+    let requiresRestart = XPIProvider.installRequiresRestart(this.addon);
+
+    logger.debug("Starting install of " + this.addon.id + " from " + this.sourceURI.spec);
+    AddonManagerPrivate.callAddonListeners("onInstalling",
+                                           this.addon.wrapper,
+                                           requiresRestart);
+
+    let stagedAddon = this.installLocation.getStagingDir();
+
+    Task.spawn((function*() {
+      let installedUnpacked = 0;
+
+      yield this.installLocation.requestStagingDir();
+
+      // remove any previously staged files
+      yield this.unstageInstall(stagedAddon);
+
+      stagedAddon.append(this.addon.id);
+      stagedAddon.leafName = this.addon.id + ".xpi";
+
+      installedUnpacked = yield this.stageInstall(requiresRestart, stagedAddon, isUpgrade);
+
+      if (requiresRestart) {
+        this.state = AddonManager.STATE_INSTALLED;
+        AddonManagerPrivate.callInstallListeners("onInstallEnded",
+                                                 this.listeners, this.wrapper,
+                                                 this.addon.wrapper);
+      }
+      else {
+        // The install is completed so it should be removed from the active list
+        XPIProvider.removeActiveInstall(this);
+
+        // Deactivate and remove the old add-on as necessary
+        let reason = BOOTSTRAP_REASONS.ADDON_INSTALL;
+        if (this.existingAddon) {
+          if (Services.vc.compare(this.existingAddon.version, this.addon.version) < 0)
+            reason = BOOTSTRAP_REASONS.ADDON_UPGRADE;
+          else
+            reason = BOOTSTRAP_REASONS.ADDON_DOWNGRADE;
+
+          if (this.existingAddon.bootstrap) {
+            let file = this.existingAddon._sourceBundle;
+            if (this.existingAddon.active) {
+              XPIProvider.callBootstrapMethod(this.existingAddon, file,
+                                              "shutdown", reason,
+                                              { newVersion: this.addon.version });
+            }
+
+            XPIProvider.callBootstrapMethod(this.existingAddon, file,
+                                            "uninstall", reason,
+                                            { newVersion: this.addon.version });
+            XPIProvider.unloadBootstrapScope(this.existingAddon.id);
+            flushChromeCaches();
+          }
+
+          if (!isUpgrade && this.existingAddon.active) {
+            XPIDatabase.updateAddonActive(this.existingAddon, false);
+          }
+        }
+
+        // Install the new add-on into its final location
+        let existingAddonID = this.existingAddon ? this.existingAddon.id : null;
+        let file = this.installLocation.installAddon({
+          id: this.addon.id,
+          source: stagedAddon,
+          existingAddonID
+        });
+
+        // Update the metadata in the database
+        this.addon._sourceBundle = file;
+        this.addon.visible = true;
+
+        if (isUpgrade) {
+          this.addon =  XPIDatabase.updateAddonMetadata(this.existingAddon, this.addon,
+                                                        file.persistentDescriptor);
+          let state = XPIStates.getAddon(this.installLocation.name, this.addon.id);
+          if (state) {
+            state.syncWithDB(this.addon, true);
+          } else {
+            logger.warn("Unexpected missing XPI state for add-on ${id}", this.addon);
+          }
+        }
+        else {
+          this.addon.active = (this.addon.visible && !this.addon.disabled);
+          this.addon = XPIDatabase.addAddonMetadata(this.addon, file.persistentDescriptor);
+          XPIStates.addAddon(this.addon);
+          this.addon.installDate = this.addon.updateDate;
+          XPIDatabase.saveChanges();
+        }
+        XPIStates.save();
+
+        let extraParams = {};
+        if (this.existingAddon) {
+          extraParams.oldVersion = this.existingAddon.version;
+        }
+
+        if (this.addon.bootstrap) {
+          XPIProvider.callBootstrapMethod(this.addon, file, "install",
+                                          reason, extraParams);
+        }
+
+        AddonManagerPrivate.callAddonListeners("onInstalled",
+                                               this.addon.wrapper);
+
+        logger.debug("Install of " + this.sourceURI.spec + " completed.");
+        this.state = AddonManager.STATE_INSTALLED;
+        AddonManagerPrivate.callInstallListeners("onInstallEnded",
+                                                 this.listeners, this.wrapper,
+                                                 this.addon.wrapper);
+
+        if (this.addon.bootstrap) {
+          if (this.addon.active) {
+            XPIProvider.callBootstrapMethod(this.addon, file, "startup",
+                                            reason, extraParams);
+          }
+          else {
+            // XXX this makes it dangerous to do some things in onInstallEnded
+            // listeners because important cleanup hasn't been done yet
+            XPIProvider.unloadBootstrapScope(this.addon.id);
+          }
+        }
+        XPIProvider.setTelemetry(this.addon.id, "unpacked", installedUnpacked);
+        recordAddonTelemetry(this.addon);
+      }
+    }).bind(this)).then(null, (e) => {
+      logger.warn(`Failed to install ${this.file.path} from ${this.sourceURI.spec} to ${stagedAddon.path}`, e);
+
+      if (stagedAddon.exists())
+        recursiveRemove(stagedAddon);
+      this.state = AddonManager.STATE_INSTALL_FAILED;
+      this.error = AddonManager.ERROR_FILE_ACCESS;
+      XPIProvider.removeActiveInstall(this);
+      AddonManagerPrivate.callAddonListeners("onOperationCancelled",
+                                             this.addon.wrapper);
+      AddonManagerPrivate.callInstallListeners("onInstallFailed",
+                                               this.listeners,
+                                               this.wrapper);
+    }).then(() => {
+      this.removeTemporaryFile();
+      return this.installLocation.releaseStagingDir();
+    });
+  }
+
+  /**
+   * Stages an upgrade for next application restart.
+   */
+  stageInstall(restartRequired, stagedAddon, isUpgrade) {
+    return Task.spawn((function*() {
+      let stagedJSON = stagedAddon.clone();
+      stagedJSON.leafName = this.addon.id + ".json";
+
+      let installedUnpacked = 0;
+
+      // First stage the file regardless of whether restarting is necessary
+      if (this.addon.unpack || Preferences.get(PREF_XPI_UNPACK, false)) {
+        logger.debug("Addon " + this.addon.id + " will be installed as " +
+                     "an unpacked directory");
+        stagedAddon.leafName = this.addon.id;
+        yield OS.File.makeDir(stagedAddon.path);
+        yield ZipUtils.extractFilesAsync(this.file, stagedAddon);
+        installedUnpacked = 1;
+      }
+      else {
+        logger.debug(`Addon ${this.addon.id} will be installed as a packed xpi`);
+        stagedAddon.leafName = this.addon.id + ".xpi";
+
+        yield OS.File.copy(this.file.path, stagedAddon.path);
+      }
+
+      if (restartRequired) {
+        // Point the add-on to its extracted files as the xpi may get deleted
+        this.addon._sourceBundle = stagedAddon;
+
+        // Cache the AddonInternal as it may have updated compatibility info
+        writeStringToFile(stagedJSON, JSON.stringify(this.addon));
+
+        logger.debug("Staged install of " + this.addon.id + " from " + this.sourceURI.spec + " ready; waiting for restart.");
+        if (isUpgrade) {
+          delete this.existingAddon.pendingUpgrade;
+          this.existingAddon.pendingUpgrade = this.addon;
+        }
+      }
+
+      return installedUnpacked;
+    }).bind(this));
+  }
+
+  /**
+   * Removes any previously staged upgrade.
+   */
+  unstageInstall(stagedAddon) {
+    return Task.spawn((function*() {
+      let stagedJSON = stagedAddon.clone();
+      let removedAddon = stagedAddon.clone();
+
+      stagedJSON.append(this.addon.id + ".json");
+
+      if (stagedJSON.exists()) {
+        stagedJSON.remove(true);
+      }
+
+      removedAddon.append(this.addon.id);
+      yield removeAsync(removedAddon);
+      removedAddon.leafName = this.addon.id + ".xpi";
+      yield removeAsync(removedAddon);
+    }).bind(this));
+  }
+
+  /**
+    * Postone a pending update, until restart or until the add-on resumes.
+    *
+    * @param {Function} resumeFunction - a function for the add-on to run
+    *                                    when resuming.
+    */
+  postpone(resumeFunction) {
+    return Task.spawn((function*() {
+      this.state = AddonManager.STATE_POSTPONED;
+
+      let stagingDir = this.installLocation.getStagingDir();
+      let stagedAddon = stagingDir.clone();
+
+      yield this.installLocation.requestStagingDir();
+      yield this.unstageInstall(stagedAddon);
+
+      stagedAddon.append(this.addon.id);
+      stagedAddon.leafName = this.addon.id + ".xpi";
+
+      yield this.stageInstall(true, stagedAddon, true);
+
+      AddonManagerPrivate.callInstallListeners("onInstallPostponed",
+                                               this.listeners, this.wrapper)
+
+      // upgrade has been staged for restart, provide a way for it to call the
+      // resume function.
+      if (resumeFunction) {
+        let callback = AddonManagerPrivate.getUpgradeListener(this.addon.id);
+        if (callback) {
+          callback({
+            version: this.version,
+            install: () => {
+              switch (this.state) {
+              case AddonManager.STATE_POSTPONED:
+                resumeFunction();
+                break;
+              default:
+                logger.warn(`${this.addon.id} cannot resume postponed upgrade from state (${this.state})`);
+                break;
+              }
+            },
+          });
+        }
+      }
+      this.installLocation.releaseStagingDir();
+    }).bind(this));
+  }
+}
+
+class LocalAddonInstall extends AddonInstall {
+  /**
+   * Initialises this install to be an install from a local file.
+   *
+   * @returns Promise
+   *          A Promise that resolves when the object is ready to use.
+   */
+  init() {
+    return Task.spawn((function*() {
+      this.file = this.sourceURI.QueryInterface(Ci.nsIFileURL).file;
+
+      if (!this.file.exists()) {
+        logger.warn("XPI file " + this.file.path + " does not exist");
+        this.state = AddonManager.STATE_DOWNLOAD_FAILED;
+        this.error = AddonManager.ERROR_NETWORK_FAILURE;
+        XPIProvider.removeActiveInstall(this);
+        return;
+      }
+
+      this.state = AddonManager.STATE_DOWNLOADED;
+      this.progress = this.file.fileSize;
+      this.maxProgress = this.file.fileSize;
+
+      if (this.hash) {
+        let crypto = Cc["@mozilla.org/security/hash;1"].
+            createInstance(Ci.nsICryptoHash);
+        try {
+          crypto.initWithString(this.hash.algorithm);
+        }
+        catch (e) {
+          logger.warn("Unknown hash algorithm '" + this.hash.algorithm + "' for addon " + this.sourceURI.spec, e);
+          this.state = AddonManager.STATE_DOWNLOAD_FAILED;
+          this.error = AddonManager.ERROR_INCORRECT_HASH;
+          XPIProvider.removeActiveInstall(this);
+          return;
+        }
+
+        let fis = Cc["@mozilla.org/network/file-input-stream;1"].
+            createInstance(Ci.nsIFileInputStream);
+        fis.init(this.file, -1, -1, false);
+        crypto.updateFromStream(fis, this.file.fileSize);
+        let calculatedHash = getHashStringForCrypto(crypto);
+        if (calculatedHash != this.hash.data) {
+          logger.warn("File hash (" + calculatedHash + ") did not match provided hash (" +
+                      this.hash.data + ")");
+          this.state = AddonManager.STATE_DOWNLOAD_FAILED;
+          this.error = AddonManager.ERROR_INCORRECT_HASH;
+          XPIProvider.removeActiveInstall(this);
+          return;
+        }
+      }
+
+      try {
+        yield this.loadManifest(this.file);
+      } catch ([error, message]) {
+        logger.warn("Invalid XPI", message);
+        this.state = AddonManager.STATE_DOWNLOAD_FAILED;
+        this.error = error;
+        XPIProvider.removeActiveInstall(this);
+        AddonManagerPrivate.callInstallListeners("onNewInstall",
+                                                 this.listeners,
+                                                 this.wrapper);
+        return;
+      }
+
+      let addon = yield new Promise(resolve => {
+        XPIDatabase.getVisibleAddonForID(this.addon.id, resolve);
+      });
+
+      this.existingAddon = addon;
+      if (addon)
+        applyBlocklistChanges(addon, this.addon);
+      this.addon.updateDate = Date.now();
+      this.addon.installDate = addon ? addon.installDate : this.addon.updateDate;
+
+      if (!this.addon.isCompatible) {
+        this.state = AddonManager.STATE_CHECKING;
+
+        yield new Promise(resolve => {
+          new UpdateChecker(this.addon, {
+            onUpdateFinished: aAddon => {
+              this.state = AddonManager.STATE_DOWNLOADED;
+              AddonManagerPrivate.callInstallListeners("onNewInstall",
+                                                       this.listeners,
+                                                       this.wrapper);
+              resolve();
+            }
+          }, AddonManager.UPDATE_WHEN_ADDON_INSTALLED);
+        });
+      }
+      else {
+        AddonManagerPrivate.callInstallListeners("onNewInstall",
+                                                 this.listeners,
+                                                 this.wrapper);
+
+      }
+    }).bind(this));
+  }
+
+  install() {
+    if (this.state == AddonManager.STATE_DOWNLOAD_FAILED) {
+      // For a local install, this state means that verification of the
+      // file failed (e.g., the hash or signature or manifest contents
+      // were invalid).  It doesn't make sense to retry anything in this
+      // case but we have callers who don't know if their AddonInstall
+      // object is a local file or a download so accomodate them here.
+      AddonManagerPrivate.callInstallListeners("onDownloadFailed",
+                                               this.listeners, this.wrapper);
+      return;
+    }
+    super.install();
+  }
+}
+
+class DownloadAddonInstall extends AddonInstall {
+  /**
+   * Instantiates a DownloadAddonInstall
+   *
+   * @param  installLocation
+   *         The InstallLocation the add-on will be installed into
+   * @param  url
+   *         The nsIURL to get the add-on from
+   * @param  name
+   *         An optional name for the add-on
+   * @param  hash
+   *         An optional hash for the add-on
+   * @param  existingAddon
+   *         The add-on this install will update if known
+   * @param  browser
+   *         The browser performing the install, used to display
+   *         authentication prompts.
+   * @param  type
+   *         An optional type for the add-on
+   * @param  icons
+   *         Optional icons for the add-on
+   * @param  version
+   *         An optional version for the add-on
+   */
+  constructor(installLocation, url, hash, existingAddon, browser,
+              name, type, icons, version) {
+    super(installLocation, url, hash, existingAddon);
+
+    this.browser = browser;
+
+    this.state = AddonManager.STATE_AVAILABLE;
+    this.name = name;
+    this.type = type;
+    this.version = version;
+    this.icons = icons;
+
+    this.stream = null;
+    this.crypto = null;
+    this.badCertHandler = null;
+    this.restartDownload = false;
+
+    AddonManagerPrivate.callInstallListeners("onNewInstall", this.listeners,
+                                            this.wrapper);
+  }
+
+  install() {
+    switch (this.state) {
+    case AddonManager.STATE_AVAILABLE:
+      this.startDownload();
+      break;
+    case AddonManager.STATE_DOWNLOAD_FAILED:
+    case AddonManager.STATE_INSTALL_FAILED:
+    case AddonManager.STATE_CANCELLED:
+      this.removeTemporaryFile();
+      this.state = AddonManager.STATE_AVAILABLE;
+      this.error = 0;
+      this.progress = 0;
+      this.maxProgress = -1;
+      this.hash = this.originalHash;
+      this.startDownload();
+      break;
+    default:
+      super.install();
+    }
+  }
+
+  cancel() {
+    if (this.state == AddonManager.STATE_DOWNLOADING) {
+      if (this.channel) {
+        logger.debug("Cancelling download of " + this.sourceURI.spec);
+        this.channel.cancel(Cr.NS_BINDING_ABORTED);
+      }
+    } else {
+      super.cancel();
+    }
+  }
+
+  observe(aSubject, aTopic, aData) {
+    // Network is going offline
+    this.cancel();
+  }
+
+  /**
+   * Starts downloading the add-on's XPI file.
+   */
+  startDownload() {
+    this.state = AddonManager.STATE_DOWNLOADING;
+    if (!AddonManagerPrivate.callInstallListeners("onDownloadStarted",
+                                                  this.listeners, this.wrapper)) {
+      logger.debug("onDownloadStarted listeners cancelled installation of addon " + this.sourceURI.spec);
+      this.state = AddonManager.STATE_CANCELLED;
+      XPIProvider.removeActiveInstall(this);
+      AddonManagerPrivate.callInstallListeners("onDownloadCancelled",
+                                               this.listeners, this.wrapper)
+      return;
+    }
+
+    // If a listener changed our state then do not proceed with the download
+    if (this.state != AddonManager.STATE_DOWNLOADING)
+      return;
+
+    if (this.channel) {
+      // A previous download attempt hasn't finished cleaning up yet, signal
+      // that it should restart when complete
+      logger.debug("Waiting for previous download to complete");
+      this.restartDownload = true;
+      return;
+    }
+
+    this.openChannel();
+  }
+
+  openChannel() {
+    this.restartDownload = false;
+
+    try {
+      this.file = getTemporaryFile();
+      this.ownsTempFile = true;
+      this.stream = Cc["@mozilla.org/network/file-output-stream;1"].
+                    createInstance(Ci.nsIFileOutputStream);
+      this.stream.init(this.file, FileUtils.MODE_WRONLY | FileUtils.MODE_CREATE |
+                       FileUtils.MODE_TRUNCATE, FileUtils.PERMS_FILE, 0);
+    }
+    catch (e) {
+      logger.warn("Failed to start download for addon " + this.sourceURI.spec, e);
+      this.state = AddonManager.STATE_DOWNLOAD_FAILED;
+      this.error = AddonManager.ERROR_FILE_ACCESS;
+      XPIProvider.removeActiveInstall(this);
+      AddonManagerPrivate.callInstallListeners("onDownloadFailed",
+                                               this.listeners, this.wrapper);
+      return;
+    }
+
+    let listener = Cc["@mozilla.org/network/stream-listener-tee;1"].
+                   createInstance(Ci.nsIStreamListenerTee);
+    listener.init(this, this.stream);
+    try {
+      let requireBuiltIn = Preferences.get(PREF_INSTALL_REQUIREBUILTINCERTS, true);
+      this.badCertHandler = new CertUtils.BadCertHandler(!requireBuiltIn);
+
+      this.channel = NetUtil.newChannel({
+        uri: this.sourceURI,
+        loadUsingSystemPrincipal: true
+      });
+      this.channel.notificationCallbacks = this;
+      if (this.channel instanceof Ci.nsIHttpChannel) {
+        this.channel.setRequestHeader("Moz-XPI-Update", "1", true);
+        if (this.channel instanceof Ci.nsIHttpChannelInternal)
+          this.channel.forceAllowThirdPartyCookie = true;
+      }
+      this.channel.asyncOpen2(listener);
+
+      Services.obs.addObserver(this, "network:offline-about-to-go-offline", false);
+    }
+    catch (e) {
+      logger.warn("Failed to start download for addon " + this.sourceURI.spec, e);
+      this.state = AddonManager.STATE_DOWNLOAD_FAILED;
+      this.error = AddonManager.ERROR_NETWORK_FAILURE;
+      XPIProvider.removeActiveInstall(this);
+      AddonManagerPrivate.callInstallListeners("onDownloadFailed",
+                                               this.listeners, this.wrapper);
+    }
+  }
+
+  /**
+   * Update the crypto hasher with the new data and call the progress listeners.
+   *
+   * @see nsIStreamListener
+   */
+  onDataAvailable(aRequest, aContext, aInputstream, aOffset, aCount) {
+    this.crypto.updateFromStream(aInputstream, aCount);
+    this.progress += aCount;
+    if (!AddonManagerPrivate.callInstallListeners("onDownloadProgress",
+                                                  this.listeners, this.wrapper)) {
+      // TODO cancel the download and make it available again (bug 553024)
+    }
+  }
+
+  /**
+   * Check the redirect response for a hash of the target XPI and verify that
+   * we don't end up on an insecure channel.
+   *
+   * @see nsIChannelEventSink
+   */
+  asyncOnChannelRedirect(aOldChannel, aNewChannel, aFlags, aCallback) {
+    if (!this.hash && aOldChannel.originalURI.schemeIs("https") &&
+        aOldChannel instanceof Ci.nsIHttpChannel) {
+      try {
+        let hashStr = aOldChannel.getResponseHeader("X-Target-Digest");
+        let hashSplit = hashStr.toLowerCase().split(":");
+        this.hash = {
+          algorithm: hashSplit[0],
+          data: hashSplit[1]
+        };
+      }
+      catch (e) {
+      }
+    }
+
+    // Verify that we don't end up on an insecure channel if we haven't got a
+    // hash to verify with (see bug 537761 for discussion)
+    if (!this.hash)
+      this.badCertHandler.asyncOnChannelRedirect(aOldChannel, aNewChannel, aFlags, aCallback);
+    else
+      aCallback.onRedirectVerifyCallback(Cr.NS_OK);
+
+    this.channel = aNewChannel;
+  }
+
+  /**
+   * This is the first chance to get at real headers on the channel.
+   *
+   * @see nsIStreamListener
+   */
+  onStartRequest(aRequest, aContext) {
+    this.crypto = Cc["@mozilla.org/security/hash;1"].
+                  createInstance(Ci.nsICryptoHash);
+    if (this.hash) {
+      try {
+        this.crypto.initWithString(this.hash.algorithm);
+      }
+      catch (e) {
+        logger.warn("Unknown hash algorithm '" + this.hash.algorithm + "' for addon " + this.sourceURI.spec, e);
+        this.state = AddonManager.STATE_DOWNLOAD_FAILED;
+        this.error = AddonManager.ERROR_INCORRECT_HASH;
+        XPIProvider.removeActiveInstall(this);
+        AddonManagerPrivate.callInstallListeners("onDownloadFailed",
+                                                 this.listeners, this.wrapper);
+        aRequest.cancel(Cr.NS_BINDING_ABORTED);
+        return;
+      }
+    }
+    else {
+      // We always need something to consume data from the inputstream passed
+      // to onDataAvailable so just create a dummy cryptohasher to do that.
+      this.crypto.initWithString("sha1");
+    }
+
+    this.progress = 0;
+    if (aRequest instanceof Ci.nsIChannel) {
+      try {
+        this.maxProgress = aRequest.contentLength;
+      }
+      catch (e) {
+      }
+      logger.debug("Download started for " + this.sourceURI.spec + " to file " +
+          this.file.path);
+    }
+  }
+
+  /**
+   * The download is complete.
+   *
+   * @see nsIStreamListener
+   */
+  onStopRequest(aRequest, aContext, aStatus) {
+    this.stream.close();
+    this.channel = null;
+    this.badCerthandler = null;
+    Services.obs.removeObserver(this, "network:offline-about-to-go-offline");
+
+    // If the download was cancelled then update the state and send events
+    if (aStatus == Cr.NS_BINDING_ABORTED) {
+      if (this.state == AddonManager.STATE_DOWNLOADING) {
+        logger.debug("Cancelled download of " + this.sourceURI.spec);
+        this.state = AddonManager.STATE_CANCELLED;
+        XPIProvider.removeActiveInstall(this);
+        AddonManagerPrivate.callInstallListeners("onDownloadCancelled",
+                                                 this.listeners, this.wrapper);
+        // If a listener restarted the download then there is no need to
+        // remove the temporary file
+        if (this.state != AddonManager.STATE_CANCELLED)
+          return;
+      }
+
+      this.removeTemporaryFile();
+      if (this.restartDownload)
+        this.openChannel();
+      return;
+    }
+
+    logger.debug("Download of " + this.sourceURI.spec + " completed.");
+
+    if (Components.isSuccessCode(aStatus)) {
+      if (!(aRequest instanceof Ci.nsIHttpChannel) || aRequest.requestSucceeded) {
+        if (!this.hash && (aRequest instanceof Ci.nsIChannel)) {
+          try {
+            CertUtils.checkCert(aRequest,
+                                !Preferences.get(PREF_INSTALL_REQUIREBUILTINCERTS, true));
+          }
+          catch (e) {
+            this.downloadFailed(AddonManager.ERROR_NETWORK_FAILURE, e);
+            return;
+          }
+        }
+
+        // convert the binary hash data to a hex string.
+        let calculatedHash = getHashStringForCrypto(this.crypto);
+        this.crypto = null;
+        if (this.hash && calculatedHash != this.hash.data) {
+          this.downloadFailed(AddonManager.ERROR_INCORRECT_HASH,
+                              "Downloaded file hash (" + calculatedHash +
+                              ") did not match provided hash (" + this.hash.data + ")");
+          return;
+        }
+
+        this.loadManifest(this.file).then(() => {
+          if (this.addon.isCompatible) {
+            this.downloadCompleted();
+          }
+          else {
+            // TODO Should we send some event here (bug 557716)?
+            this.state = AddonManager.STATE_CHECKING;
+            new UpdateChecker(this.addon, {
+              onUpdateFinished: aAddon => this.downloadCompleted(),
+            }, AddonManager.UPDATE_WHEN_ADDON_INSTALLED);
+          }
+        }, ([error, message]) => {
+          this.removeTemporaryFile();
+          this.downloadFailed(error, message);
+        });
+      }
+      else if (aRequest instanceof Ci.nsIHttpChannel) {
+        this.downloadFailed(AddonManager.ERROR_NETWORK_FAILURE,
+                            aRequest.responseStatus + " " +
+                            aRequest.responseStatusText);
+      }
+      else {
+        this.downloadFailed(AddonManager.ERROR_NETWORK_FAILURE, aStatus);
+      }
+    }
+    else {
+      this.downloadFailed(AddonManager.ERROR_NETWORK_FAILURE, aStatus);
+    }
+  }
+
+  /**
+   * Notify listeners that the download failed.
+   *
+   * @param  aReason
+   *         Something to log about the failure
+   * @param  error
+   *         The error code to pass to the listeners
+   */
+  downloadFailed(aReason, aError) {
+    logger.warn("Download of " + this.sourceURI.spec + " failed", aError);
+    this.state = AddonManager.STATE_DOWNLOAD_FAILED;
+    this.error = aReason;
+    XPIProvider.removeActiveInstall(this);
+    AddonManagerPrivate.callInstallListeners("onDownloadFailed", this.listeners,
+                                             this.wrapper);
+
+    // If the listener hasn't restarted the download then remove any temporary
+    // file
+    if (this.state == AddonManager.STATE_DOWNLOAD_FAILED) {
+      logger.debug("downloadFailed: removing temp file for " + this.sourceURI.spec);
+      this.removeTemporaryFile();
+    }
+    else
+      logger.debug("downloadFailed: listener changed AddonInstall state for " +
+          this.sourceURI.spec + " to " + this.state);
+  }
+
+  /**
+   * Notify listeners that the download completed.
+   */
+  downloadCompleted() {
+    XPIDatabase.getVisibleAddonForID(this.addon.id, aAddon => {
+      if (aAddon)
+        this.existingAddon = aAddon;
+
+      this.state = AddonManager.STATE_DOWNLOADED;
+      this.addon.updateDate = Date.now();
+
+      if (this.existingAddon) {
+        this.addon.existingAddonID = this.existingAddon.id;
+        this.addon.installDate = this.existingAddon.installDate;
+        applyBlocklistChanges(this.existingAddon, this.addon);
+      }
+      else {
+        this.addon.installDate = this.addon.updateDate;
+      }
+
+      if (AddonManagerPrivate.callInstallListeners("onDownloadEnded",
+                                                   this.listeners,
+                                                   this.wrapper)) {
+        // If a listener changed our state then do not proceed with the install
+        if (this.state != AddonManager.STATE_DOWNLOADED)
+          return;
+
+        // If an upgrade listener is registered for this add-on, pass control
+        // over the upgrade to the add-on.
+        if (AddonManagerPrivate.hasUpgradeListener(this.addon.id)) {
+          logger.info(`add-on ${this.addon.id} has an upgrade listener, postponing upgrade until restart`);
+          let resumeFn = () => {
+            logger.info(`${this.addon.id} has resumed a previously postponed upgrade`);
+            this.state = AddonManager.STATE_DOWNLOADED;
+            this.install();
+          }
+          this.postpone(resumeFn);
+        } else {
+          // no upgrade listener present, so proceed with normal install
+          this.install();
+          if (this.linkedInstalls) {
+            for (let install of this.linkedInstalls) {
+              if (install.state == AddonManager.STATE_DOWNLOADED)
+                install.install();
+            }
+          }
+        }
+      }
+    });
+  }
+
+  getInterface(iid) {
+    if (iid.equals(Ci.nsIAuthPrompt2)) {
+      let win = null;
+      if (this.browser) {
+        win = this.browser.contentWindow || this.browser.ownerDocument.defaultView;
+      }
+
+      let factory = Cc["@mozilla.org/prompter;1"].
+                    getService(Ci.nsIPromptFactory);
+      let prompt = factory.getPrompt(win, Ci.nsIAuthPrompt2);
+
+      if (this.browser && prompt instanceof Ci.nsILoginManagerPrompter)
+        prompt.browser = this.browser;
+
+      return prompt;
+    }
+    else if (iid.equals(Ci.nsIChannelEventSink)) {
+      return this;
+    }
+
+    return this.badCertHandler.getInterface(iid);
+  }
+
+  /**
+    * Postone a pending update, until restart or until the add-on resumes.
+    *
+    * @param {Function} resumeFn - a function for the add-on to run
+    *                                    when resuming.
+    */
+  postpone(resumeFn) {
+    return Task.spawn((function*() {
+      this.state = AddonManager.STATE_POSTPONED;
+
+      let stagingDir = this.installLocation.getStagingDir();
+      let stagedAddon = stagingDir.clone();
+
+      yield this.installLocation.requestStagingDir();
+      yield this.unstageInstall(stagedAddon);
+
+      stagedAddon.append(this.addon.id);
+      stagedAddon.leafName = this.addon.id + ".xpi";
+
+      yield this.stageInstall(true, stagedAddon, true);
+
+      AddonManagerPrivate.callInstallListeners("onInstallPostponed",
+                                               this.listeners, this.wrapper)
+
+      // upgrade has been staged for restart, provide a way for it to call the
+      // resume function.
+      let callback = AddonManagerPrivate.getUpgradeListener(this.addon.id);
+      if (callback) {
+        callback({
+          version: this.version,
+          install: () => {
+            switch (this.state) {
+            case AddonManager.STATE_POSTPONED:
+              if (resumeFn) {
+                resumeFn();
+              }
+              break;
+            default:
+              logger.warn(`${this.addon.id} cannot resume postponed upgrade from state (${this.state})`);
+              break;
+            }
+          },
+        });
+      }
+      // Release the staging directory lock, but since the staging dir is populated
+      // it will not be removed until resumed or installed by restart.
+      // See also cleanStagingDir()
+      this.installLocation.releaseStagingDir();
+    }).bind(this));
+  }
+}
+
+/**
+ * This class exists just for the specific case of staged add-ons that
+ * fail to install at startup.  When that happens, the add-on remains
+ * staged but we want to keep track of it like other installs so that we
+ * can clean it up if the same add-on is installed again (see the comment
+ * about "pending installs for the same add-on" in AddonInstall.startInstall)
+ */
+class StagedAddonInstall extends AddonInstall {
+  constructor(installLocation, dir, manifest) {
+    super(installLocation, dir);
+
+    this.name = manifest.name;
+    this.type = manifest.type;
+    this.version = manifest.version;
+    this.icons = manifest.icons;
+    this.releaseNotesURI = manifest.releaseNotesURI ?
+                           NetUtil.newURI(manifest.releaseNotesURI) :
+                           null;
+    this.sourceURI = manifest.sourceURI ?
+                     NetUtil.newURI(manifest.sourceURI) :
+                     null;
+    this.file = null;
+    this.addon = manifest;
+
+    this.state = AddonManager.STATE_INSTALLED;
+  }
+}
+
+/**
+ * Creates a new AddonInstall to install an add-on from a local file.
+ *
+ * @param  file
+ *         The file to install
+ * @param  location
+ *         The location to install to
+ * @returns Promise
+ *          A Promise that resolves with the new install object.
+ */
+function createLocalInstall(file, location) {
+  if (!location) {
+    location = XPIProvider.installLocationsByName[KEY_APP_PROFILE];
+  }
+  let url = Services.io.newFileURI(file);
+
+  try {
+    let install = new LocalAddonInstall(location, url);
+    return install.init().then(() => install);
+  }
+  catch (e) {
+    logger.error("Error creating install", e);
+    XPIProvider.removeActiveInstall(this);
+    return Promise.resolve(null);
+  }
+}
+
+/**
+ * Creates a new AddonInstall to download and install a URL.
+ *
+ * @param  aCallback
+ *         The callback to pass the new AddonInstall to
+ * @param  aUri
+ *         The URI to download
+ * @param  aHash
+ *         A hash for the add-on
+ * @param  aName
+ *         A name for the add-on
+ * @param  aIcons
+ *         An icon URLs for the add-on
+ * @param  aVersion
+ *         A version for the add-on
+ * @param  aBrowser
+ *         The browser performing the install
+ */
+function createDownloadInstall(aCallback, aUri, aHash, aName, aIcons,
+                               aVersion, aBrowser) {
+  let location = XPIProvider.installLocationsByName[KEY_APP_PROFILE];
+  let url = NetUtil.newURI(aUri);
+
+  if (url instanceof Ci.nsIFileURL) {
+    let install = new LocalAddonInstall(location, url, aHash);
+    install.init().then(() => { aCallback(install); });
+  } else {
+    let install = new DownloadAddonInstall(location, url, aHash, null,
+                                           aBrowser, aName, null, aIcons,
+                                           aVersion);
+    aCallback(install);
+  }
+}
+
+/**
+ * Creates a new AddonInstall for an update.
+ *
+ * @param  aCallback
+ *         The callback to pass the new AddonInstall to
+ * @param  aAddon
+ *         The add-on being updated
+ * @param  aUpdate
+ *         The metadata about the new version from the update manifest
+ */
+function createUpdate(aCallback, aAddon, aUpdate) {
+  let url = NetUtil.newURI(aUpdate.updateURL);
+
+  Task.spawn(function*() {
+    let install;
+    if (url instanceof Ci.nsIFileURL) {
+      install = new LocalAddonInstall(aAddon._installLocation, url,
+                                      aUpdate.updateHash, aAddon);
+      yield install.init();
+    } else {
+      install = new DownloadAddonInstall(aAddon._installLocation, url,
+                                         aUpdate.updateHash, aAddon, null,
+                                         aAddon.selectedLocale.name, aAddon.type,
+                                         aAddon.icons, aUpdate.version);
+    }
+    try {
+      if (aUpdate.updateInfoURL)
+        install.releaseNotesURI = NetUtil.newURI(escapeAddonURI(aAddon, aUpdate.updateInfoURL));
+    }
+    catch (e) {
+      // If the releaseNotesURI cannot be parsed then just ignore it.
+    }
+
+    aCallback(install);
+  });
+}
+
+// This map is shared between AddonInstallWrapper and AddonWrapper
+const wrapperMap = new WeakMap();
+let installFor = wrapper => wrapperMap.get(wrapper);
+let addonFor = installFor;
+
+/**
+ * Creates a wrapper for an AddonInstall that only exposes the public API
+ *
+ * @param  install
+ *         The AddonInstall to create a wrapper for
+ */
+function AddonInstallWrapper(aInstall) {
+  wrapperMap.set(this, aInstall);
+}
+
+AddonInstallWrapper.prototype = {
+  get __AddonInstallInternal__() {
+    return AppConstants.DEBUG ? installFor(this) : undefined;
+  },
+
+  get type() {
+    return getExternalType(installFor(this).type);
+  },
+
+  get iconURL() {
+    return installFor(this).icons[32];
+  },
+
+  get existingAddon() {
+    let install = installFor(this);
+    return install.existingAddon ? install.existingAddon.wrapper : null;
+  },
+
+  get addon() {
+    let install = installFor(this);
+    return install.addon ? install.addon.wrapper : null;
+  },
+
+  get sourceURI() {
+    return installFor(this).sourceURI;
+  },
+
+  get linkedInstalls() {
+    let install = installFor(this);
+    if (!install.linkedInstalls)
+      return null;
+    return install.linkedInstalls.map(i => i.wrapper);
+  },
+
+  install: function() {
+    installFor(this).install();
+  },
+
+  cancel: function() {
+    installFor(this).cancel();
+  },
+
+  addListener: function(listener) {
+    installFor(this).addListener(listener);
+  },
+
+  removeListener: function(listener) {
+    installFor(this).removeListener(listener);
+  },
+};
+
+["name", "version", "icons", "releaseNotesURI", "file", "state", "error",
+ "progress", "maxProgress", "certificate", "certName"].forEach(function(aProp) {
+  Object.defineProperty(AddonInstallWrapper.prototype, aProp, {
+    get: function() {
+      return installFor(this)[aProp];
+    },
+    enumerable: true,
+  });
+});
+
+/**
+ * Creates a new update checker.
+ *
+ * @param  aAddon
+ *         The add-on to check for updates
+ * @param  aListener
+ *         An UpdateListener to notify of updates
+ * @param  aReason
+ *         The reason for the update check
+ * @param  aAppVersion
+ *         An optional application version to check for updates for
+ * @param  aPlatformVersion
+ *         An optional platform version to check for updates for
+ * @throws if the aListener or aReason arguments are not valid
+ */
+function UpdateChecker(aAddon, aListener, aReason, aAppVersion, aPlatformVersion) {
+  if (!aListener || !aReason)
+    throw Cr.NS_ERROR_INVALID_ARG;
+
+  Components.utils.import("resource://gre/modules/addons/AddonUpdateChecker.jsm");
+
+  this.addon = aAddon;
+  aAddon._updateCheck = this;
+  XPIProvider.doing(this);
+  this.listener = aListener;
+  this.appVersion = aAppVersion;
+  this.platformVersion = aPlatformVersion;
+  this.syncCompatibility = (aReason == AddonManager.UPDATE_WHEN_NEW_APP_INSTALLED);
+
+  let updateURL = aAddon.updateURL;
+  if (!updateURL) {
+    if (aReason == AddonManager.UPDATE_WHEN_PERIODIC_UPDATE &&
+        Services.prefs.getPrefType(PREF_EM_UPDATE_BACKGROUND_URL) == Services.prefs.PREF_STRING) {
+      updateURL = Services.prefs.getCharPref(PREF_EM_UPDATE_BACKGROUND_URL);
+    } else {
+      updateURL = Services.prefs.getCharPref(PREF_EM_UPDATE_URL);
+    }
+  }
+
+  const UPDATE_TYPE_COMPATIBILITY = 32;
+  const UPDATE_TYPE_NEWVERSION = 64;
+
+  aReason |= UPDATE_TYPE_COMPATIBILITY;
+  if ("onUpdateAvailable" in this.listener)
+    aReason |= UPDATE_TYPE_NEWVERSION;
+
+  let url = escapeAddonURI(aAddon, updateURL, aReason, aAppVersion);
+  this._parser = AddonUpdateChecker.checkForUpdates(aAddon.id, aAddon.updateKey,
+                                                    url, this);
+}
+
+UpdateChecker.prototype = {
+  addon: null,
+  listener: null,
+  appVersion: null,
+  platformVersion: null,
+  syncCompatibility: null,
+
+  /**
+   * Calls a method on the listener passing any number of arguments and
+   * consuming any exceptions.
+   *
+   * @param  aMethod
+   *         The method to call on the listener
+   */
+  callListener: function(aMethod, ...aArgs) {
+    if (!(aMethod in this.listener))
+      return;
+
+    try {
+      this.listener[aMethod].apply(this.listener, aArgs);
+    }
+    catch (e) {
+      logger.warn("Exception calling UpdateListener method " + aMethod, e);
+    }
+  },
+
+  /**
+   * Called when AddonUpdateChecker completes the update check
+   *
+   * @param  updates
+   *         The list of update details for the add-on
+   */
+  onUpdateCheckComplete: function(aUpdates) {
+    XPIProvider.done(this.addon._updateCheck);
+    this.addon._updateCheck = null;
+    let AUC = AddonUpdateChecker;
+
+    let ignoreMaxVersion = false;
+    let ignoreStrictCompat = false;
+    if (!AddonManager.checkCompatibility) {
+      ignoreMaxVersion = true;
+      ignoreStrictCompat = true;
+    } else if (this.addon.type in COMPATIBLE_BY_DEFAULT_TYPES &&
+               !AddonManager.strictCompatibility &&
+               !this.addon.strictCompatibility &&
+               !this.addon.hasBinaryComponents) {
+      ignoreMaxVersion = true;
+    }
+
+    // Always apply any compatibility update for the current version
+    let compatUpdate = AUC.getCompatibilityUpdate(aUpdates, this.addon.version,
+                                                  this.syncCompatibility,
+                                                  null, null,
+                                                  ignoreMaxVersion,
+                                                  ignoreStrictCompat);
+    // Apply the compatibility update to the database
+    if (compatUpdate)
+      this.addon.applyCompatibilityUpdate(compatUpdate, this.syncCompatibility);
+
+    // If the request is for an application or platform version that is
+    // different to the current application or platform version then look for a
+    // compatibility update for those versions.
+    if ((this.appVersion &&
+         Services.vc.compare(this.appVersion, Services.appinfo.version) != 0) ||
+        (this.platformVersion &&
+         Services.vc.compare(this.platformVersion, Services.appinfo.platformVersion) != 0)) {
+      compatUpdate = AUC.getCompatibilityUpdate(aUpdates, this.addon.version,
+                                                false, this.appVersion,
+                                                this.platformVersion,
+                                                ignoreMaxVersion,
+                                                ignoreStrictCompat);
+    }
+
+    if (compatUpdate)
+      this.callListener("onCompatibilityUpdateAvailable", this.addon.wrapper);
+    else
+      this.callListener("onNoCompatibilityUpdateAvailable", this.addon.wrapper);
+
+    function sendUpdateAvailableMessages(aSelf, aInstall) {
+      if (aInstall) {
+        aSelf.callListener("onUpdateAvailable", aSelf.addon.wrapper,
+                           aInstall.wrapper);
+      }
+      else {
+        aSelf.callListener("onNoUpdateAvailable", aSelf.addon.wrapper);
+      }
+      aSelf.callListener("onUpdateFinished", aSelf.addon.wrapper,
+                         AddonManager.UPDATE_STATUS_NO_ERROR);
+    }
+
+    let compatOverrides = AddonManager.strictCompatibility ?
+                            null :
+                            this.addon.compatibilityOverrides;
+
+    let update = AUC.getNewestCompatibleUpdate(aUpdates,
+                                           this.appVersion,
+                                           this.platformVersion,
+                                           ignoreMaxVersion,
+                                           ignoreStrictCompat,
+                                           compatOverrides);
+
+    if (update && Services.vc.compare(this.addon.version, update.version) < 0
+        && !this.addon._installLocation.locked) {
+      for (let currentInstall of XPIProvider.installs) {
+        // Skip installs that don't match the available update
+        if (currentInstall.existingAddon != this.addon ||
+            currentInstall.version != update.version)
+          continue;
+
+        // If the existing install has not yet started downloading then send an
+        // available update notification. If it is already downloading then
+        // don't send any available update notification
+        if (currentInstall.state == AddonManager.STATE_AVAILABLE) {
+          logger.debug("Found an existing AddonInstall for " + this.addon.id);
+          sendUpdateAvailableMessages(this, currentInstall);
+        }
+        else
+          sendUpdateAvailableMessages(this, null);
+        return;
+      }
+
+      createUpdate(aInstall => {
+        sendUpdateAvailableMessages(this, aInstall);
+      }, this.addon, update);
+    }
+    else {
+      sendUpdateAvailableMessages(this, null);
+    }
+  },
+
+  /**
+   * Called when AddonUpdateChecker fails the update check
+   *
+   * @param  aError
+   *         An error status
+   */
+  onUpdateCheckError: function(aError) {
+    XPIProvider.done(this.addon._updateCheck);
+    this.addon._updateCheck = null;
+    this.callListener("onNoCompatibilityUpdateAvailable", this.addon.wrapper);
+    this.callListener("onNoUpdateAvailable", this.addon.wrapper);
+    this.callListener("onUpdateFinished", this.addon.wrapper, aError);
+  },
+
+  /**
+   * Called to cancel an in-progress update check
+   */
+  cancel: function() {
+    let parser = this._parser;
+    if (parser) {
+      this._parser = null;
+      // This will call back to onUpdateCheckError with a CANCELLED error
+      parser.cancel();
+    }
+  }
+};
+
+/**
+ * The AddonInternal is an internal only representation of add-ons. It may
+ * have come from the database (see DBAddonInternal in XPIProviderUtils.jsm)
+ * or an install manifest.
+ */
+function AddonInternal() {
+  this._hasResourceCache = new Map();
+
+  XPCOMUtils.defineLazyGetter(this, "wrapper", () => {
+    return new AddonWrapper(this);
+  });
+}
+
+AddonInternal.prototype = {
+  _selectedLocale: null,
+  _hasResourceCache: null,
+  active: false,
+  visible: false,
+  userDisabled: false,
+  appDisabled: false,
+  softDisabled: false,
+  sourceURI: null,
+  releaseNotesURI: null,
+  foreignInstall: false,
+  seen: true,
+  skinnable: false,
+
+  /**
+   * @property {Array<string>} dependencies
+   *   An array of bootstrapped add-on IDs on which this add-on depends.
+   *   The add-on will remain appDisabled if any of the dependent
+   *   add-ons is not installed and enabled.
+   */
+  dependencies: Object.freeze([]),
+  hasEmbeddedWebExtension: false,
+
+  get selectedLocale() {
+    if (this._selectedLocale)
+      return this._selectedLocale;
+    let locale = Locale.findClosestLocale(this.locales);
+    this._selectedLocale = locale ? locale : this.defaultLocale;
+    return this._selectedLocale;
+  },
+
+  get providesUpdatesSecurely() {
+    return !!(this.updateKey || !this.updateURL ||
+              this.updateURL.substring(0, 6) == "https:");
+  },
+
+  get isCorrectlySigned() {
+    switch (this._installLocation.name) {
+      case KEY_APP_SYSTEM_ADDONS:
+        // System add-ons must be signed by the system key.
+        return this.signedState == AddonManager.SIGNEDSTATE_SYSTEM
+
+      case KEY_APP_SYSTEM_DEFAULTS:
+      case KEY_APP_TEMPORARY:
+        // Temporary and built-in system add-ons do not require signing.
+        return true;
+
+      case KEY_APP_SYSTEM_SHARE:
+      case KEY_APP_SYSTEM_LOCAL:
+        // On UNIX platforms except OSX, an additional location for system
+        // add-ons exists in /usr/{lib,share}/mozilla/extensions. Add-ons
+        // installed there do not require signing.
+        if (Services.appinfo.OS != "Darwin")
+          return true;
+        break;
+    }
+
+    if (this.signedState === AddonManager.SIGNEDSTATE_NOT_REQUIRED)
+      return true;
+    return this.signedState > AddonManager.SIGNEDSTATE_MISSING;
+  },
+
+  get isCompatible() {
+    return this.isCompatibleWith();
+  },
+
+  get disabled() {
+    return (this.userDisabled || this.appDisabled || this.softDisabled);
+  },
+
+  get isPlatformCompatible() {
+    if (this.targetPlatforms.length == 0)
+      return true;
+
+    let matchedOS = false;
+
+    // If any targetPlatform matches the OS and contains an ABI then we will
+    // only match a targetPlatform that contains both the current OS and ABI
+    let needsABI = false;
+
+    // Some platforms do not specify an ABI, test against null in that case.
+    let abi = null;
+    try {
+      abi = Services.appinfo.XPCOMABI;
+    }
+    catch (e) { }
+
+    // Something is causing errors in here
+    try {
+      for (let platform of this.targetPlatforms) {
+        if (platform.os == Services.appinfo.OS) {
+          if (platform.abi) {
+            needsABI = true;
+            if (platform.abi === abi)
+              return true;
+          }
+          else {
+            matchedOS = true;
+          }
+        }
+      }
+    } catch (e) {
+      let message = "Problem with addon " + this.id + " targetPlatforms "
+                    + JSON.stringify(this.targetPlatforms);
+      logger.error(message, e);
+      AddonManagerPrivate.recordException("XPI", message, e);
+      // don't trust this add-on
+      return false;
+    }
+
+    return matchedOS && !needsABI;
+  },
+
+  isCompatibleWith: function(aAppVersion, aPlatformVersion) {
+    let app = this.matchingTargetApplication;
+    if (!app)
+      return false;
+
+    // set reasonable defaults for minVersion and maxVersion
+    let minVersion = app.minVersion || "0";
+    let maxVersion = app.maxVersion || "*";
+
+    if (!aAppVersion)
+      aAppVersion = Services.appinfo.version;
+    if (!aPlatformVersion)
+      aPlatformVersion = Services.appinfo.platformVersion;
+
+    let version;
+    if (app.id == Services.appinfo.ID)
+      version = aAppVersion;
+    else if (app.id == TOOLKIT_ID)
+      version = aPlatformVersion
+
+    // Only extensions and dictionaries can be compatible by default; themes
+    // and language packs always use strict compatibility checking.
+    if (this.type in COMPATIBLE_BY_DEFAULT_TYPES &&
+        !AddonManager.strictCompatibility && !this.strictCompatibility &&
+        !this.hasBinaryComponents) {
+
+      // The repository can specify compatibility overrides.
+      // Note: For now, only blacklisting is supported by overrides.
+      if (this._repositoryAddon &&
+          this._repositoryAddon.compatibilityOverrides) {
+        let overrides = this._repositoryAddon.compatibilityOverrides;
+        let override = AddonRepository.findMatchingCompatOverride(this.version,
+                                                                  overrides);
+        if (override && override.type == "incompatible")
+          return false;
+      }
+
+      // Extremely old extensions should not be compatible by default.
+      let minCompatVersion;
+      if (app.id == Services.appinfo.ID)
+        minCompatVersion = XPIProvider.minCompatibleAppVersion;
+      else if (app.id == TOOLKIT_ID)
+        minCompatVersion = XPIProvider.minCompatiblePlatformVersion;
+
+      if (minCompatVersion &&
+          Services.vc.compare(minCompatVersion, maxVersion) > 0)
+        return false;
+
+      return Services.vc.compare(version, minVersion) >= 0;
+    }
+
+    return (Services.vc.compare(version, minVersion) >= 0) &&
+           (Services.vc.compare(version, maxVersion) <= 0)
+  },
+
+  get matchingTargetApplication() {
+    let app = null;
+    for (let targetApp of this.targetApplications) {
+      if (targetApp.id == Services.appinfo.ID)
+        return targetApp;
+      if (targetApp.id == TOOLKIT_ID)
+        app = targetApp;
+    }
+    return app;
+  },
+
+  get blocklistState() {
+    let staticItem = findMatchingStaticBlocklistItem(this);
+    if (staticItem)
+      return staticItem.level;
+
+    return Blocklist.getAddonBlocklistState(this.wrapper);
+  },
+
+  get blocklistURL() {
+    let staticItem = findMatchingStaticBlocklistItem(this);
+    if (staticItem) {
+      let url = Services.urlFormatter.formatURLPref("extensions.blocklist.itemURL");
+      return url.replace(/%blockID%/g, staticItem.blockID);
+    }
+
+    return Blocklist.getAddonBlocklistURL(this.wrapper);
+  },
+
+  applyCompatibilityUpdate: function(aUpdate, aSyncCompatibility) {
+    for (let targetApp of this.targetApplications) {
+      for (let updateTarget of aUpdate.targetApplications) {
+        if (targetApp.id == updateTarget.id && (aSyncCompatibility ||
+            Services.vc.compare(targetApp.maxVersion, updateTarget.maxVersion) < 0)) {
+          targetApp.minVersion = updateTarget.minVersion;
+          targetApp.maxVersion = updateTarget.maxVersion;
+        }
+      }
+    }
+    if (aUpdate.multiprocessCompatible !== undefined)
+      this.multiprocessCompatible = aUpdate.multiprocessCompatible;
+    this.appDisabled = !isUsableAddon(this);
+  },
+
+  /**
+   * getDataDirectory tries to execute the callback with two arguments:
+   * 1) the path of the data directory within the profile,
+   * 2) any exception generated from trying to build it.
+   */
+  getDataDirectory: function(callback) {
+    let parentPath = OS.Path.join(OS.Constants.Path.profileDir, "extension-data");
+    let dirPath = OS.Path.join(parentPath, this.id);
+
+    Task.spawn(function*() {
+      yield OS.File.makeDir(parentPath, {ignoreExisting: true});
+      yield OS.File.makeDir(dirPath, {ignoreExisting: true});
+    }).then(() => callback(dirPath, null),
+            e => callback(dirPath, e));
+  },
+
+  /**
+   * toJSON is called by JSON.stringify in order to create a filtered version
+   * of this object to be serialized to a JSON file. A new object is returned
+   * with copies of all non-private properties. Functions, getters and setters
+   * are not copied.
+   *
+   * @param  aKey
+   *         The key that this object is being serialized as in the JSON.
+   *         Unused here since this is always the main object serialized
+   *
+   * @return an object containing copies of the properties of this object
+   *         ignoring private properties, functions, getters and setters
+   */
+  toJSON: function(aKey) {
+    let obj = {};
+    for (let prop in this) {
+      // Ignore the wrapper property
+      if (prop == "wrapper")
+        continue;
+
+      // Ignore private properties
+      if (prop.substring(0, 1) == "_")
+        continue;
+
+      // Ignore getters
+      if (this.__lookupGetter__(prop))
+        continue;
+
+      // Ignore setters
+      if (this.__lookupSetter__(prop))
+        continue;
+
+      // Ignore functions
+      if (typeof this[prop] == "function")
+        continue;
+
+      obj[prop] = this[prop];
+    }
+
+    return obj;
+  },
+
+  /**
+   * When an add-on install is pending its metadata will be cached in a file.
+   * This method reads particular properties of that metadata that may be newer
+   * than that in the install manifest, like compatibility information.
+   *
+   * @param  aObj
+   *         A JS object containing the cached metadata
+   */
+  importMetadata: function(aObj) {
+    for (let prop of PENDING_INSTALL_METADATA) {
+      if (!(prop in aObj))
+        continue;
+
+      this[prop] = aObj[prop];
+    }
+
+    // Compatibility info may have changed so update appDisabled
+    this.appDisabled = !isUsableAddon(this);
+  },
+
+  permissions: function() {
+    let permissions = 0;
+
+    // Add-ons that aren't installed cannot be modified in any way
+    if (!(this.inDatabase))
+      return permissions;
+
+    if (!this.appDisabled) {
+      if (this.userDisabled || this.softDisabled) {
+        permissions |= AddonManager.PERM_CAN_ENABLE;
+      }
+      else if (this.type != "theme") {
+        permissions |= AddonManager.PERM_CAN_DISABLE;
+      }
+    }
+
+    // Add-ons that are in locked install locations, or are pending uninstall
+    // cannot be upgraded or uninstalled
+    if (!this._installLocation.locked && !this.pendingUninstall) {
+      // Experiments cannot be upgraded.
+      // System add-on upgrades are triggered through a different mechanism (see updateSystemAddons())
+      let isSystem = (this._installLocation.name == KEY_APP_SYSTEM_DEFAULTS ||
+                      this._installLocation.name == KEY_APP_SYSTEM_ADDONS);
+      // Add-ons that are installed by a file link cannot be upgraded.
+      if (this.type != "experiment" &&
+          !this._installLocation.isLinkedAddon(this.id) && !isSystem) {
+        permissions |= AddonManager.PERM_CAN_UPGRADE;
+      }
+
+      permissions |= AddonManager.PERM_CAN_UNINSTALL;
+    }
+
+    return permissions;
+  },
+};
+
+/**
+ * The AddonWrapper wraps an Addon to provide the data visible to consumers of
+ * the public API.
+ */
+function AddonWrapper(aAddon) {
+  wrapperMap.set(this, aAddon);
+}
+
+AddonWrapper.prototype = {
+  get __AddonInternal__() {
+    return AppConstants.DEBUG ? addonFor(this) : undefined;
+  },
+
+  get seen() {
+    return addonFor(this).seen;
+  },
+
+  get hasEmbeddedWebExtension() {
+    return addonFor(this).hasEmbeddedWebExtension;
+  },
+
+  markAsSeen: function() {
+    addonFor(this).seen = true;
+    XPIDatabase.saveChanges();
+  },
+
+  get type() {
+    return getExternalType(addonFor(this).type);
+  },
+
+  get isWebExtension() {
+    return addonFor(this).type == "webextension";
+  },
+
+  get temporarilyInstalled() {
+    return addonFor(this)._installLocation == TemporaryInstallLocation;
+  },
+
+  get aboutURL() {
+    return this.isActive ? addonFor(this)["aboutURL"] : null;
+  },
+
+  get optionsURL() {
+    if (!this.isActive) {
+      return null;
+    }
+
+    let addon = addonFor(this);
+    if (addon.optionsURL) {
+      if (this.isWebExtension || this.hasEmbeddedWebExtension) {
+        // The internal object's optionsURL property comes from the addons
+        // DB and should be a relative URL.  However, extensions with
+        // options pages installed before bug 1293721 was fixed got absolute
+        // URLs in the addons db.  This code handles both cases.
+        let base = ExtensionManagement.getURLForExtension(addon.id);
+        if (!base) {
+          return null;
+        }
+        return new URL(addon.optionsURL, base).href;
+      }
+      return addon.optionsURL;
+    }
+
+    if (this.hasResource("options.xul"))
+      return this.getResourceURI("options.xul").spec;
+
+    return null;
+  },
+
+  get optionsType() {
+    if (!this.isActive)
+      return null;
+
+    let addon = addonFor(this);
+    let hasOptionsXUL = this.hasResource("options.xul");
+    let hasOptionsURL = !!this.optionsURL;
+
+    if (addon.optionsType) {
+      switch (parseInt(addon.optionsType, 10)) {
+      case AddonManager.OPTIONS_TYPE_DIALOG:
+      case AddonManager.OPTIONS_TYPE_TAB:
+        return hasOptionsURL ? addon.optionsType : null;
+      case AddonManager.OPTIONS_TYPE_INLINE:
+      case AddonManager.OPTIONS_TYPE_INLINE_INFO:
+      case AddonManager.OPTIONS_TYPE_INLINE_BROWSER:
+        return (hasOptionsXUL || hasOptionsURL) ? addon.optionsType : null;
+      }
+      return null;
+    }
+
+    if (hasOptionsXUL)
+      return AddonManager.OPTIONS_TYPE_INLINE;
+
+    if (hasOptionsURL)
+      return AddonManager.OPTIONS_TYPE_DIALOG;
+
+    return null;
+  },
+
+  get iconURL() {
+    return AddonManager.getPreferredIconURL(this, 48);
+  },
+
+  get icon64URL() {
+    return AddonManager.getPreferredIconURL(this, 64);
+  },
+
+  get icons() {
+    let addon = addonFor(this);
+    let icons = {};
+
+    if (addon._repositoryAddon) {
+      for (let size in addon._repositoryAddon.icons) {
+        icons[size] = addon._repositoryAddon.icons[size];
+      }
+    }
+
+    if (addon.icons) {
+      for (let size in addon.icons) {
+        icons[size] = this.getResourceURI(addon.icons[size]).spec;
+      }
+    } else {
+      // legacy add-on that did not update its icon data yet
+      if (this.hasResource("icon.png")) {
+        icons[32] = icons[48] = this.getResourceURI("icon.png").spec;
+      }
+      if (this.hasResource("icon64.png")) {
+        icons[64] = this.getResourceURI("icon64.png").spec;
+      }
+    }
+
+    if (this.isActive && addon.iconURL) {
+      icons[32] = addon.iconURL;
+      icons[48] = addon.iconURL;
+    }
+
+    if (this.isActive && addon.icon64URL) {
+      icons[64] = addon.icon64URL;
+    }
+
+    Object.freeze(icons);
+    return icons;
+  },
+
+  get screenshots() {
+    let addon = addonFor(this);
+    let repositoryAddon = addon._repositoryAddon;
+    if (repositoryAddon && ("screenshots" in repositoryAddon)) {
+      let repositoryScreenshots = repositoryAddon.screenshots;
+      if (repositoryScreenshots && repositoryScreenshots.length > 0)
+        return repositoryScreenshots;
+    }
+
+    if (addon.type == "theme" && this.hasResource("preview.png")) {
+      let url = this.getResourceURI("preview.png").spec;
+      return [new AddonManagerPrivate.AddonScreenshot(url)];
+    }
+
+    return null;
+  },
+
+  get applyBackgroundUpdates() {
+    return addonFor(this).applyBackgroundUpdates;
+  },
+  set applyBackgroundUpdates(val) {
+    let addon = addonFor(this);
+    if (this.type == "experiment") {
+      logger.warn("Setting applyBackgroundUpdates on an experiment is not supported.");
+      return addon.applyBackgroundUpdates;
+    }
+
+    if (val != AddonManager.AUTOUPDATE_DEFAULT &&
+        val != AddonManager.AUTOUPDATE_DISABLE &&
+        val != AddonManager.AUTOUPDATE_ENABLE) {
+      val = val ? AddonManager.AUTOUPDATE_DEFAULT :
+                  AddonManager.AUTOUPDATE_DISABLE;
+    }
+
+    if (val == addon.applyBackgroundUpdates)
+      return val;
+
+    XPIDatabase.setAddonProperties(addon, {
+      applyBackgroundUpdates: val
+    });
+    AddonManagerPrivate.callAddonListeners("onPropertyChanged", this, ["applyBackgroundUpdates"]);
+
+    return val;
+  },
+
+  set syncGUID(val) {
+    let addon = addonFor(this);
+    if (addon.syncGUID == val)
+      return val;
+
+    if (addon.inDatabase)
+      XPIDatabase.setAddonSyncGUID(addon, val);
+
+    addon.syncGUID = val;
+
+    return val;
+  },
+
+  get install() {
+    let addon = addonFor(this);
+    if (!("_install" in addon) || !addon._install)
+      return null;
+    return addon._install.wrapper;
+  },
+
+  get pendingUpgrade() {
+    let addon = addonFor(this);
+    return addon.pendingUpgrade ? addon.pendingUpgrade.wrapper : null;
+  },
+
+  get scope() {
+    let addon = addonFor(this);
+    if (addon._installLocation)
+      return addon._installLocation.scope;
+
+    return AddonManager.SCOPE_PROFILE;
+  },
+
+  get pendingOperations() {
+    let addon = addonFor(this);
+    let pending = 0;
+    if (!(addon.inDatabase)) {
+      // Add-on is pending install if there is no associated install (shouldn't
+      // happen here) or if the install is in the process of or has successfully
+      // completed the install. If an add-on is pending install then we ignore
+      // any other pending operations.
+      if (!addon._install || addon._install.state == AddonManager.STATE_INSTALLING ||
+          addon._install.state == AddonManager.STATE_INSTALLED)
+        return AddonManager.PENDING_INSTALL;
+    }
+    else if (addon.pendingUninstall) {
+      // If an add-on is pending uninstall then we ignore any other pending
+      // operations
+      return AddonManager.PENDING_UNINSTALL;
+    }
+
+    if (addon.active && addon.disabled)
+      pending |= AddonManager.PENDING_DISABLE;
+    else if (!addon.active && !addon.disabled)
+      pending |= AddonManager.PENDING_ENABLE;
+
+    if (addon.pendingUpgrade)
+      pending |= AddonManager.PENDING_UPGRADE;
+
+    return pending;
+  },
+
+  get operationsRequiringRestart() {
+    let addon = addonFor(this);
+    let ops = 0;
+    if (XPIProvider.installRequiresRestart(addon))
+      ops |= AddonManager.OP_NEEDS_RESTART_INSTALL;
+    if (XPIProvider.uninstallRequiresRestart(addon))
+      ops |= AddonManager.OP_NEEDS_RESTART_UNINSTALL;
+    if (XPIProvider.enableRequiresRestart(addon))
+      ops |= AddonManager.OP_NEEDS_RESTART_ENABLE;
+    if (XPIProvider.disableRequiresRestart(addon))
+      ops |= AddonManager.OP_NEEDS_RESTART_DISABLE;
+
+    return ops;
+  },
+
+  get isDebuggable() {
+    return this.isActive && addonFor(this).bootstrap;
+  },
+
+  get permissions() {
+    return addonFor(this).permissions();
+  },
+
+  get isActive() {
+    let addon = addonFor(this);
+    if (!addon.active)
+      return false;
+    if (!Services.appinfo.inSafeMode)
+      return true;
+    return addon.bootstrap && canRunInSafeMode(addon);
+  },
+
+  get userDisabled() {
+    let addon = addonFor(this);
+    return addon.softDisabled || addon.userDisabled;
+  },
+  set userDisabled(val) {
+    let addon = addonFor(this);
+    if (val == this.userDisabled) {
+      return val;
+    }
+
+    if (addon.inDatabase) {
+      if (addon.type == "theme" && val) {
+        if (addon.internalName == XPIProvider.defaultSkin)
+          throw new Error("Cannot disable the default theme");
+        XPIProvider.enableDefaultTheme();
+      }
+      else {
+        // hidden and system add-ons should not be user disasbled,
+        // as there is no UI to re-enable them.
+        if (this.hidden) {
+          throw new Error(`Cannot disable hidden add-on ${addon.id}`);
+        }
+        XPIProvider.updateAddonDisabledState(addon, val);
+      }
+    }
+    else {
+      addon.userDisabled = val;
+      // When enabling remove the softDisabled flag
+      if (!val)
+        addon.softDisabled = false;
+    }
+
+    return val;
+  },
+
+  set softDisabled(val) {
+    let addon = addonFor(this);
+    if (val == addon.softDisabled)
+      return val;
+
+    if (addon.inDatabase) {
+      // When softDisabling a theme just enable the active theme
+      if (addon.type == "theme" && val && !addon.userDisabled) {
+        if (addon.internalName == XPIProvider.defaultSkin)
+          throw new Error("Cannot disable the default theme");
+        XPIProvider.enableDefaultTheme();
+      }
+      else {
+        XPIProvider.updateAddonDisabledState(addon, undefined, val);
+      }
+    }
+    else if (!addon.userDisabled) {
+      // Only set softDisabled if not already disabled
+      addon.softDisabled = val;
+    }
+
+    return val;
+  },
+
+  get hidden() {
+    let addon = addonFor(this);
+    if (addon._installLocation.name == KEY_APP_TEMPORARY)
+      return false;
+
+    return (addon._installLocation.name == KEY_APP_SYSTEM_DEFAULTS ||
+            addon._installLocation.name == KEY_APP_SYSTEM_ADDONS);
+  },
+
+  get isSystem() {
+    let addon = addonFor(this);
+    return (addon._installLocation.name == KEY_APP_SYSTEM_DEFAULTS ||
+            addon._installLocation.name == KEY_APP_SYSTEM_ADDONS);
+  },
+
+  // Returns true if Firefox Sync should sync this addon. Only non-hotfixes
+  // directly in the profile are considered syncable.
+  get isSyncable() {
+    let addon = addonFor(this);
+    let hotfixID = Preferences.get(PREF_EM_HOTFIX_ID, undefined);
+    if (hotfixID && hotfixID == addon.id) {
+      return false;
+    }
+    return (addon._installLocation.name == KEY_APP_PROFILE);
+  },
+
+  isCompatibleWith: function(aAppVersion, aPlatformVersion) {
+    return addonFor(this).isCompatibleWith(aAppVersion, aPlatformVersion);
+  },
+
+  uninstall: function(alwaysAllowUndo) {
+    let addon = addonFor(this);
+    XPIProvider.uninstallAddon(addon, alwaysAllowUndo);
+  },
+
+  cancelUninstall: function() {
+    let addon = addonFor(this);
+    XPIProvider.cancelUninstallAddon(addon);
+  },
+
+  findUpdates: function(aListener, aReason, aAppVersion, aPlatformVersion) {
+    // Short-circuit updates for experiments because updates are handled
+    // through the Experiments Manager.
+    if (this.type == "experiment") {
+      AddonManagerPrivate.callNoUpdateListeners(this, aListener, aReason,
+                                                aAppVersion, aPlatformVersion);
+      return;
+    }
+
+    new UpdateChecker(addonFor(this), aListener, aReason, aAppVersion, aPlatformVersion);
+  },
+
+  // Returns true if there was an update in progress, false if there was no update to cancel
+  cancelUpdate: function() {
+    let addon = addonFor(this);
+    if (addon._updateCheck) {
+      addon._updateCheck.cancel();
+      return true;
+    }
+    return false;
+  },
+
+  hasResource: function(aPath) {
+    let addon = addonFor(this);
+    if (addon._hasResourceCache.has(aPath))
+      return addon._hasResourceCache.get(aPath);
+
+    let bundle = addon._sourceBundle.clone();
+
+    // Bundle may not exist any more if the addon has just been uninstalled,
+    // but explicitly first checking .exists() results in unneeded file I/O.
+    try {
+      var isDir = bundle.isDirectory();
+    } catch (e) {
+      addon._hasResourceCache.set(aPath, false);
+      return false;
+    }
+
+    if (isDir) {
+      if (aPath)
+        aPath.split("/").forEach(part => bundle.append(part));
+      let result = bundle.exists();
+      addon._hasResourceCache.set(aPath, result);
+      return result;
+    }
+
+    let zipReader = Cc["@mozilla.org/libjar/zip-reader;1"].
+                    createInstance(Ci.nsIZipReader);
+    try {
+      zipReader.open(bundle);
+      let result = zipReader.hasEntry(aPath);
+      addon._hasResourceCache.set(aPath, result);
+      return result;
+    }
+    catch (e) {
+      addon._hasResourceCache.set(aPath, false);
+      return false;
+    }
+    finally {
+      zipReader.close();
+    }
+  },
+
+  /**
+   * Reloads the add-on.
+   *
+   * For temporarily installed add-ons, this uninstalls and re-installs the
+   * add-on. Otherwise, the addon is disabled and then re-enabled, and the cache
+   * is flushed.
+   *
+   * @return Promise
+   */
+  reload: function() {
+    return new Promise((resolve) => {
+      const addon = addonFor(this);
+
+      logger.debug(`reloading add-on ${addon.id}`);
+
+      if (!this.temporarilyInstalled) {
+        let addonFile = addon.getResourceURI;
+        XPIProvider.updateAddonDisabledState(addon, true);
+        Services.obs.notifyObservers(addonFile, "flush-cache-entry", null);
+        XPIProvider.updateAddonDisabledState(addon, false)
+        resolve();
+      } else {
+        // This function supports re-installing an existing add-on.
+        resolve(AddonManager.installTemporaryAddon(addon._sourceBundle));
+      }
+    });
+  },
+
+  /**
+   * Returns a URI to the selected resource or to the add-on bundle if aPath
+   * is null. URIs to the bundle will always be file: URIs. URIs to resources
+   * will be file: URIs if the add-on is unpacked or jar: URIs if the add-on is
+   * still an XPI file.
+   *
+   * @param  aPath
+   *         The path in the add-on to get the URI for or null to get a URI to
+   *         the file or directory the add-on is installed as.
+   * @return an nsIURI
+   */
+  getResourceURI: function(aPath) {
+    let addon = addonFor(this);
+    if (!aPath)
+      return NetUtil.newURI(addon._sourceBundle);
+
+    return getURIForResourceInFile(addon._sourceBundle, aPath);
+  }
+};
+
+/**
+ * The PrivateWrapper is used to expose certain functionality only when being
+ * called with the add-on instanceID, disallowing other add-ons to access it.
+ */
+function PrivateWrapper(aAddon) {
+  AddonWrapper.call(this, aAddon);
+}
+
+PrivateWrapper.prototype = Object.create(AddonWrapper.prototype);
+Object.assign(PrivateWrapper.prototype, {
+  addonId() {
+    return this.id;
+  },
+
+  /**
+   * Retrieves the preferred global context to be used from the
+   * add-on debugging window.
+   *
+   * @returns  global
+   *         The object set as global context. Must be a window object.
+   */
+  getDebugGlobal(global) {
+    let activeAddon = XPIProvider.activeAddons.get(this.id);
+    if (activeAddon) {
+      return activeAddon.debugGlobal;
+    }
+
+    return null;
+  },
+
+  /**
+   * Defines a global context to be used in the console
+   * of the add-on debugging window.
+   *
+   * @param  global
+   *         The object to set as global context. Must be a window object.
+   */
+  setDebugGlobal(global) {
+    if (!global) {
+      // If the new global is null, notify the listeners regardless
+      // from the current state of the addon.
+      // NOTE: this happen after the addon has been disabled and
+      // the global will never be set to null otherwise.
+      AddonManagerPrivate.callAddonListeners("onPropertyChanged",
+                                             addonFor(this),
+                                             ["debugGlobal"]);
+    } else {
+      let activeAddon = XPIProvider.activeAddons.get(this.id);
+      if (activeAddon) {
+        let globalChanged = activeAddon.debugGlobal != global;
+        activeAddon.debugGlobal = global;
+
+        if (globalChanged) {
+          AddonManagerPrivate.callAddonListeners("onPropertyChanged",
+                                                 addonFor(this),
+                                                 ["debugGlobal"]);
+        }
+      }
+    }
+  }
+});
+
+function chooseValue(aAddon, aObj, aProp) {
+  let repositoryAddon = aAddon._repositoryAddon;
+  let objValue = aObj[aProp];
+
+  if (repositoryAddon && (aProp in repositoryAddon) &&
+      (objValue === undefined || objValue === null)) {
+    return [repositoryAddon[aProp], true];
+  }
+
+  return [objValue, false];
+}
+
+function defineAddonWrapperProperty(name, getter) {
+  Object.defineProperty(AddonWrapper.prototype, name, {
+    get: getter,
+    enumerable: true,
+  });
+}
+
+["id", "syncGUID", "version", "isCompatible", "isPlatformCompatible",
+ "providesUpdatesSecurely", "blocklistState", "blocklistURL", "appDisabled",
+ "softDisabled", "skinnable", "size", "foreignInstall", "hasBinaryComponents",
+ "strictCompatibility", "compatibilityOverrides", "updateURL", "dependencies",
+ "getDataDirectory", "multiprocessCompatible", "signedState", "mpcOptedOut",
+ "isCorrectlySigned"].forEach(function(aProp) {
+   defineAddonWrapperProperty(aProp, function() {
+     let addon = addonFor(this);
+     return (aProp in addon) ? addon[aProp] : undefined;
+   });
+});
+
+["fullDescription", "developerComments", "eula", "supportURL",
+ "contributionURL", "contributionAmount", "averageRating", "reviewCount",
+ "reviewURL", "totalDownloads", "weeklyDownloads", "dailyUsers",
+ "repositoryStatus"].forEach(function(aProp) {
+  defineAddonWrapperProperty(aProp, function() {
+    let addon = addonFor(this);
+    if (addon._repositoryAddon)
+      return addon._repositoryAddon[aProp];
+
+    return null;
+  });
+});
+
+["installDate", "updateDate"].forEach(function(aProp) {
+  defineAddonWrapperProperty(aProp, function() {
+    return new Date(addonFor(this)[aProp]);
+  });
+});
+
+["sourceURI", "releaseNotesURI"].forEach(function(aProp) {
+  defineAddonWrapperProperty(aProp, function() {
+    let addon = addonFor(this);
+
+    // Temporary Installed Addons do not have a "sourceURI",
+    // But we can use the "_sourceBundle" as an alternative,
+    // which points to the path of the addon xpi installed
+    // or its source dir (if it has been installed from a
+    // directory).
+    if (aProp == "sourceURI" && this.temporarilyInstalled) {
+      return Services.io.newFileURI(addon._sourceBundle);
+    }
+
+    let [target, fromRepo] = chooseValue(addon, addon, aProp);
+    if (!target)
+      return null;
+    if (fromRepo)
+      return target;
+    return NetUtil.newURI(target);
+  });
+});
+
+PROP_LOCALE_SINGLE.forEach(function(aProp) {
+  defineAddonWrapperProperty(aProp, function() {
+    let addon = addonFor(this);
+    // Override XPI creator if repository creator is defined
+    if (aProp == "creator" &&
+        addon._repositoryAddon && addon._repositoryAddon.creator) {
+      return addon._repositoryAddon.creator;
+    }
+
+    let result = null;
+
+    if (addon.active) {
+      try {
+        let pref = PREF_EM_EXTENSION_FORMAT + addon.id + "." + aProp;
+        let value = Preferences.get(pref, null, Ci.nsIPrefLocalizedString);
+        if (value)
+          result = value;
+      }
+      catch (e) {
+      }
+    }
+
+    let rest;
+    if (result == null)
+      [result, ...rest] = chooseValue(addon, addon.selectedLocale, aProp);
+
+    if (aProp == "creator")
+      return result ? new AddonManagerPrivate.AddonAuthor(result) : null;
+
+    return result;
+  });
+});
+
+PROP_LOCALE_MULTI.forEach(function(aProp) {
+  defineAddonWrapperProperty(aProp, function() {
+    let addon = addonFor(this);
+    let results = null;
+    let usedRepository = false;
+
+    if (addon.active) {
+      let pref = PREF_EM_EXTENSION_FORMAT + addon.id + "." +
+                 aProp.substring(0, aProp.length - 1);
+      let list = Services.prefs.getChildList(pref, {});
+      if (list.length > 0) {
+        list.sort();
+        results = [];
+        for (let childPref of list) {
+          let value = Preferences.get(childPref, null, Ci.nsIPrefLocalizedString);
+          if (value)
+            results.push(value);
+        }
+      }
+    }
+
+    if (results == null)
+      [results, usedRepository] = chooseValue(addon, addon.selectedLocale, aProp);
+
+    if (results && !usedRepository) {
+      results = results.map(function(aResult) {
+        return new AddonManagerPrivate.AddonAuthor(aResult);
+      });
+    }
+
+    return results;
+  });
+});
+
+/**
+ * An object which identifies a directory install location for add-ons. The
+ * location consists of a directory which contains the add-ons installed in the
+ * location.
+ *
+ * Each add-on installed in the location is either a directory containing the
+ * add-on's files or a text file containing an absolute path to the directory
+ * containing the add-ons files. The directory or text file must have the same
+ * name as the add-on's ID.
+ *
+ * @param  aName
+ *         The string identifier for the install location
+ * @param  aDirectory
+ *         The nsIFile directory for the install location
+ * @param  aScope
+ *         The scope of add-ons installed in this location
+ */
+function DirectoryInstallLocation(aName, aDirectory, aScope) {
+  this._name = aName;
+  this.locked = true;
+  this._directory = aDirectory;
+  this._scope = aScope
+  this._IDToFileMap = {};
+  this._linkedAddons = [];
+
+  if (!aDirectory || !aDirectory.exists())
+    return;
+  if (!aDirectory.isDirectory())
+    throw new Error("Location must be a directory.");
+
+  this._readAddons();
+}
+
+DirectoryInstallLocation.prototype = {
+  _name       : "",
+  _directory   : null,
+  _IDToFileMap : null,  // mapping from add-on ID to nsIFile
+
+  /**
+   * Reads a directory linked to in a file.
+   *
+   * @param   file
+   *          The file containing the directory path
+   * @return  An nsIFile object representing the linked directory.
+   */
+  _readDirectoryFromFile: function(aFile) {
+    let linkedDirectory;
+    if (aFile.isSymlink()) {
+      linkedDirectory = aFile.clone();
+      try {
+        linkedDirectory.normalize();
+      } catch (e) {
+        logger.warn("Symbolic link " + aFile.path + " points to a path" +
+             " which does not exist");
+        return null;
+      }
+    }
+    else {
+      let fis = Cc["@mozilla.org/network/file-input-stream;1"].
+                createInstance(Ci.nsIFileInputStream);
+      fis.init(aFile, -1, -1, false);
+      let line = { value: "" };
+      if (fis instanceof Ci.nsILineInputStream)
+        fis.readLine(line);
+      fis.close();
+      if (line.value) {
+        linkedDirectory = Cc["@mozilla.org/file/local;1"].
+                              createInstance(Ci.nsIFile);
+
+        try {
+          linkedDirectory.initWithPath(line.value);
+        }
+        catch (e) {
+          linkedDirectory.setRelativeDescriptor(aFile.parent, line.value);
+        }
+      }
+    }
+
+    if (linkedDirectory) {
+      if (!linkedDirectory.exists()) {
+        logger.warn("File pointer " + aFile.path + " points to " + linkedDirectory.path +
+             " which does not exist");
+        return null;
+      }
+
+      if (!linkedDirectory.isDirectory()) {
+        logger.warn("File pointer " + aFile.path + " points to " + linkedDirectory.path +
+             " which is not a directory");
+        return null;
+      }
+
+      return linkedDirectory;
+    }
+
+    logger.warn("File pointer " + aFile.path + " does not contain a path");
+    return null;
+  },
+
+  /**
+   * Finds all the add-ons installed in this location.
+   */
+  _readAddons: function() {
+    // Use a snapshot of the directory contents to avoid possible issues with
+    // iterating over a directory while removing files from it (the YAFFS2
+    // embedded filesystem has this issue, see bug 772238).
+    let entries = getDirectoryEntries(this._directory);
+    for (let entry of entries) {
+      let id = entry.leafName;
+
+      if (id == DIR_STAGE || id == DIR_TRASH)
+        continue;
+
+      let directLoad = false;
+      if (entry.isFile() &&
+          id.substring(id.length - 4).toLowerCase() == ".xpi") {
+        directLoad = true;
+        id = id.substring(0, id.length - 4);
+      }
+
+      if (!gIDTest.test(id)) {
+        logger.debug("Ignoring file entry whose name is not a valid add-on ID: " +
+             entry.path);
+        continue;
+      }
+
+      if (!directLoad && (entry.isFile() || entry.isSymlink())) {
+        let newEntry = this._readDirectoryFromFile(entry);
+        if (!newEntry) {
+          logger.debug("Deleting stale pointer file " + entry.path);
+          try {
+            entry.remove(true);
+          }
+          catch (e) {
+            logger.warn("Failed to remove stale pointer file " + entry.path, e);
+            // Failing to remove the stale pointer file is ignorable
+          }
+          continue;
+        }
+
+        entry = newEntry;
+        this._linkedAddons.push(id);
+      }
+
+      this._IDToFileMap[id] = entry;
+      XPIProvider._addURIMapping(id, entry);
+    }
+  },
+
+  /**
+   * Gets the name of this install location.
+   */
+  get name() {
+    return this._name;
+  },
+
+  /**
+   * Gets the scope of this install location.
+   */
+  get scope() {
+    return this._scope;
+  },
+
+  /**
+   * Gets an array of nsIFiles for add-ons installed in this location.
+   */
+  getAddonLocations: function() {
+    let locations = new Map();
+    for (let id in this._IDToFileMap) {
+      locations.set(id, this._IDToFileMap[id].clone());
+    }
+    return locations;
+  },
+
+  /**
+   * Gets the directory that the add-on with the given ID is installed in.
+   *
+   * @param  aId
+   *         The ID of the add-on
+   * @return The nsIFile
+   * @throws if the ID does not match any of the add-ons installed
+   */
+  getLocationForID: function(aId) {
+    if (aId in this._IDToFileMap)
+      return this._IDToFileMap[aId].clone();
+    throw new Error("Unknown add-on ID " + aId);
+  },
+
+  /**
+   * Returns true if the given addon was installed in this location by a text
+   * file pointing to its real path.
+   *
+   * @param aId
+   *        The ID of the addon
+   */
+  isLinkedAddon: function(aId) {
+    return this._linkedAddons.indexOf(aId) != -1;
+  }
+};
+
+/**
+ * An extension of DirectoryInstallLocation which adds methods to installing
+ * and removing add-ons from the directory at runtime.
+ *
+ * @param  aName
+ *         The string identifier for the install location
+ * @param  aDirectory
+ *         The nsIFile directory for the install location
+ * @param  aScope
+ *         The scope of add-ons installed in this location
+ */
+function MutableDirectoryInstallLocation(aName, aDirectory, aScope) {
+  DirectoryInstallLocation.call(this, aName, aDirectory, aScope);
+  this.locked = false;
+  this._stagingDirLock = 0;
+}
+
+MutableDirectoryInstallLocation.prototype = Object.create(DirectoryInstallLocation.prototype);
+Object.assign(MutableDirectoryInstallLocation.prototype, {
+  /**
+   * Gets the staging directory to put add-ons that are pending install and
+   * uninstall into.
+   *
+   * @return an nsIFile
+   */
+  getStagingDir: function() {
+    let dir = this._directory.clone();
+    dir.append(DIR_STAGE);
+    return dir;
+  },
+
+  requestStagingDir: function() {
+    this._stagingDirLock++;
+
+    if (this._stagingDirPromise)
+      return this._stagingDirPromise;
+
+    OS.File.makeDir(this._directory.path);
+    let stagepath = OS.Path.join(this._directory.path, DIR_STAGE);
+    return this._stagingDirPromise = OS.File.makeDir(stagepath).then(null, (e) => {
+      if (e instanceof OS.File.Error && e.becauseExists)
+        return;
+      logger.error("Failed to create staging directory", e);
+      throw e;
+    });
+  },
+
+  releaseStagingDir: function() {
+    this._stagingDirLock--;
+
+    if (this._stagingDirLock == 0) {
+      this._stagingDirPromise = null;
+      this.cleanStagingDir();
+    }
+
+    return Promise.resolve();
+  },
+
+  /**
+   * Removes the specified files or directories in the staging directory and
+   * then if the staging directory is empty attempts to remove it.
+   *
+   * @param  aLeafNames
+   *         An array of file or directory to remove from the directory, the
+   *         array may be empty
+   */
+  cleanStagingDir: function(aLeafNames = []) {
+    let dir = this.getStagingDir();
+
+    for (let name of aLeafNames) {
+      let file = dir.clone();
+      file.append(name);
+      recursiveRemove(file);
+    }
+
+    if (this._stagingDirLock > 0)
+      return;
+
+    let dirEntries = dir.directoryEntries.QueryInterface(Ci.nsIDirectoryEnumerator);
+    try {
+      if (dirEntries.nextFile)
+        return;
+    }
+    finally {
+      dirEntries.close();
+    }
+
+    try {
+      setFilePermissions(dir, FileUtils.PERMS_DIRECTORY);
+      dir.remove(false);
+    }
+    catch (e) {
+      logger.warn("Failed to remove staging dir", e);
+      // Failing to remove the staging directory is ignorable
+    }
+  },
+
+  /**
+   * Returns a directory that is normally on the same filesystem as the rest of
+   * the install location and can be used for temporarily storing files during
+   * safe move operations. Calling this method will delete the existing trash
+   * directory and its contents.
+   *
+   * @return an nsIFile
+   */
+  getTrashDir: function() {
+    let trashDir = this._directory.clone();
+    trashDir.append(DIR_TRASH);
+    let trashDirExists = trashDir.exists();
+    try {
+      if (trashDirExists)
+        recursiveRemove(trashDir);
+      trashDirExists = false;
+    } catch (e) {
+      logger.warn("Failed to remove trash directory", e);
+    }
+    if (!trashDirExists)
+      trashDir.create(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+
+    return trashDir;
+  },
+
+  /**
+   * Installs an add-on into the install location.
+   *
+   * @param  id
+   *         The ID of the add-on to install
+   * @param  source
+   *         The source nsIFile to install from
+   * @param  existingAddonID
+   *         The ID of an existing add-on to uninstall at the same time
+   * @param  action
+   *         What to we do with the given source file:
+   *           "move"
+   *           Default action, the source files will be moved to the new
+   *           location,
+   *           "copy"
+   *           The source files will be copied,
+   *           "proxy"
+   *           A "proxy file" is going to refer to the source file path
+   * @return an nsIFile indicating where the add-on was installed to
+   */
+  installAddon: function({ id, source, existingAddonID, action = "move" }) {
+    let trashDir = this.getTrashDir();
+
+    let transaction = new SafeInstallOperation();
+
+    let moveOldAddon = aId => {
+      let file = this._directory.clone();
+      file.append(aId);
+
+      if (file.exists())
+        transaction.moveUnder(file, trashDir);
+
+      file = this._directory.clone();
+      file.append(aId + ".xpi");
+      if (file.exists()) {
+        flushJarCache(file);
+        transaction.moveUnder(file, trashDir);
+      }
+    }
+
+    // If any of these operations fails the finally block will clean up the
+    // temporary directory
+    try {
+      moveOldAddon(id);
+      if (existingAddonID && existingAddonID != id) {
+        moveOldAddon(existingAddonID);
+
+        {
+          // Move the data directories.
+          /* XXX ajvincent We can't use OS.File:  installAddon isn't compatible
+           * with Promises, nor is SafeInstallOperation.  Bug 945540 has been filed
+           * for porting to OS.File.
+           */
+          let oldDataDir = FileUtils.getDir(
+            KEY_PROFILEDIR, ["extension-data", existingAddonID], false, true
+          );
+
+          if (oldDataDir.exists()) {
+            let newDataDir = FileUtils.getDir(
+              KEY_PROFILEDIR, ["extension-data", id], false, true
+            );
+            if (newDataDir.exists()) {
+              let trashData = trashDir.clone();
+              trashData.append("data-directory");
+              transaction.moveUnder(newDataDir, trashData);
+            }
+
+            transaction.moveTo(oldDataDir, newDataDir);
+          }
+        }
+      }
+
+      if (action == "copy") {
+        transaction.copy(source, this._directory);
+      }
+      else if (action == "move") {
+        if (source.isFile())
+          flushJarCache(source);
+
+        transaction.moveUnder(source, this._directory);
+      }
+      // Do nothing for the proxy file as we sideload an addon permanently
+    }
+    finally {
+      // It isn't ideal if this cleanup fails but it isn't worth rolling back
+      // the install because of it.
+      try {
+        recursiveRemove(trashDir);
+      }
+      catch (e) {
+        logger.warn("Failed to remove trash directory when installing " + id, e);
+      }
+    }
+
+    let newFile = this._directory.clone();
+
+    if (action == "proxy") {
+      // When permanently installing sideloaded addon, we just put a proxy file
+      // refering to the addon sources
+      newFile.append(id);
+
+      writeStringToFile(newFile, source.path);
+    } else {
+      newFile.append(source.leafName);
+    }
+
+    try {
+      newFile.lastModifiedTime = Date.now();
+    } catch (e)  {
+      logger.warn("failed to set lastModifiedTime on " + newFile.path, e);
+    }
+    this._IDToFileMap[id] = newFile;
+    XPIProvider._addURIMapping(id, newFile);
+
+    if (existingAddonID && existingAddonID != id &&
+        existingAddonID in this._IDToFileMap) {
+      delete this._IDToFileMap[existingAddonID];
+    }
+
+    return newFile;
+  },
+
+  /**
+   * Uninstalls an add-on from this location.
+   *
+   * @param  aId
+   *         The ID of the add-on to uninstall
+   * @throws if the ID does not match any of the add-ons installed
+   */
+  uninstallAddon: function(aId) {
+    let file = this._IDToFileMap[aId];
+    if (!file) {
+      logger.warn("Attempted to remove " + aId + " from " +
+           this._name + " but it was already gone");
+      return;
+    }
+
+    file = this._directory.clone();
+    file.append(aId);
+    if (!file.exists())
+      file.leafName += ".xpi";
+
+    if (!file.exists()) {
+      logger.warn("Attempted to remove " + aId + " from " +
+           this._name + " but it was already gone");
+
+      delete this._IDToFileMap[aId];
+      return;
+    }
+
+    let trashDir = this.getTrashDir();
+
+    if (file.leafName != aId) {
+      logger.debug("uninstallAddon: flushing jar cache " + file.path + " for addon " + aId);
+      flushJarCache(file);
+    }
+
+    let transaction = new SafeInstallOperation();
+
+    try {
+      transaction.moveUnder(file, trashDir);
+    }
+    finally {
+      // It isn't ideal if this cleanup fails, but it is probably better than
+      // rolling back the uninstall at this point
+      try {
+        recursiveRemove(trashDir);
+      }
+      catch (e) {
+        logger.warn("Failed to remove trash directory when uninstalling " + aId, e);
+      }
+    }
+
+    delete this._IDToFileMap[aId];
+  },
+});
+
+/**
+ * An object which identifies a directory install location for system add-ons
+ * upgrades.
+ *
+ * The location consists of a directory which contains the add-ons installed.
+ *
+ * @param  aName
+ *         The string identifier for the install location
+ * @param  aDirectory
+ *         The nsIFile directory for the install location
+ * @param  aScope
+ *         The scope of add-ons installed in this location
+ * @param  aResetSet
+ *         True to throw away the current add-on set
+ */
+function SystemAddonInstallLocation(aName, aDirectory, aScope, aResetSet) {
+  this._baseDir = aDirectory;
+  this._nextDir = null;
+
+  this._stagingDirLock = 0;
+
+  if (aResetSet)
+    this.resetAddonSet();
+
+  this._addonSet = this._loadAddonSet();
+
+  this._directory = null;
+  if (this._addonSet.directory) {
+    this._directory = aDirectory.clone();
+    this._directory.append(this._addonSet.directory);
+    logger.info("SystemAddonInstallLocation scanning directory " + this._directory.path);
+  }
+  else {
+    logger.info("SystemAddonInstallLocation directory is missing");
+  }
+
+  DirectoryInstallLocation.call(this, aName, this._directory, aScope);
+  this.locked = false;
+}
+
+SystemAddonInstallLocation.prototype = Object.create(DirectoryInstallLocation.prototype);
+Object.assign(SystemAddonInstallLocation.prototype, {
+  /**
+   * Removes the specified files or directories in the staging directory and
+   * then if the staging directory is empty attempts to remove it.
+   *
+   * @param  aLeafNames
+   *         An array of file or directory to remove from the directory, the
+   *         array may be empty
+   */
+  cleanStagingDir: function(aLeafNames = []) {
+    let dir = this.getStagingDir();
+
+    for (let name of aLeafNames) {
+      let file = dir.clone();
+      file.append(name);
+      recursiveRemove(file);
+    }
+
+    if (this._stagingDirLock > 0)
+      return;
+
+    let dirEntries = dir.directoryEntries.QueryInterface(Ci.nsIDirectoryEnumerator);
+    try {
+      if (dirEntries.nextFile)
+        return;
+    }
+    finally {
+      dirEntries.close();
+    }
+
+    try {
+      setFilePermissions(dir, FileUtils.PERMS_DIRECTORY);
+      dir.remove(false);
+    }
+    catch (e) {
+      logger.warn("Failed to remove staging dir", e);
+      // Failing to remove the staging directory is ignorable
+    }
+  },
+
+  /**
+   * Gets the staging directory to put add-ons that are pending install and
+   * uninstall into.
+   *
+   * @return {nsIFile} - staging directory for system add-on upgrades.
+   */
+  getStagingDir: function() {
+    this._addonSet = this._loadAddonSet();
+    let dir = null;
+    if (this._addonSet.directory) {
+      this._directory = this._baseDir.clone();
+      this._directory.append(this._addonSet.directory);
+      dir = this._directory.clone();
+      dir.append(DIR_STAGE);
+    }
+    else {
+      logger.info("SystemAddonInstallLocation directory is missing");
+    }
+
+    return dir;
+  },
+
+  requestStagingDir: function() {
+    this._stagingDirLock++;
+    if (this._stagingDirPromise)
+      return this._stagingDirPromise;
+
+    this._addonSet = this._loadAddonSet();
+    if (this._addonSet.directory) {
+      this._directory = this._baseDir.clone();
+      this._directory.append(this._addonSet.directory);
+    }
+
+    OS.File.makeDir(this._directory.path);
+    let stagepath = OS.Path.join(this._directory.path, DIR_STAGE);
+    return this._stagingDirPromise = OS.File.makeDir(stagepath).then(null, (e) => {
+      if (e instanceof OS.File.Error && e.becauseExists)
+        return;
+      logger.error("Failed to create staging directory", e);
+      throw e;
+    });
+  },
+
+  releaseStagingDir: function() {
+    this._stagingDirLock--;
+
+    if (this._stagingDirLock == 0) {
+      this._stagingDirPromise = null;
+      this.cleanStagingDir();
+    }
+
+    return Promise.resolve();
+  },
+
+  /**
+   * Reads the current set of system add-ons
+   */
+  _loadAddonSet: function() {
+    try {
+      let setStr = Preferences.get(PREF_SYSTEM_ADDON_SET, null);
+      if (setStr) {
+        let addonSet = JSON.parse(setStr);
+        if ((typeof addonSet == "object") && addonSet.schema == 1)
+          return addonSet;
+      }
+    }
+    catch (e) {
+      logger.error("Malformed system add-on set, resetting.");
+    }
+
+    return { schema: 1, addons: {} };
+  },
+
+  /**
+   * Saves the current set of system add-ons
+   *
+   * @param {Object} aAddonSet - object containing schema, directory and set
+   *                 of system add-on IDs and versions.
+   */
+  _saveAddonSet: function(aAddonSet) {
+    Preferences.set(PREF_SYSTEM_ADDON_SET, JSON.stringify(aAddonSet));
+  },
+
+  getAddonLocations: function() {
+    // Updated system add-ons are ignored in safe mode
+    if (Services.appinfo.inSafeMode)
+      return new Map();
+
+    let addons = DirectoryInstallLocation.prototype.getAddonLocations.call(this);
+
+    // Strip out any unexpected add-ons from the list
+    for (let id of addons.keys()) {
+      if (!(id in this._addonSet.addons))
+        addons.delete(id);
+    }
+
+    return addons;
+  },
+
+  /**
+   * Tests whether updated system add-ons are expected.
+   */
+  isActive: function() {
+    return this._directory != null;
+  },
+
+  isValidAddon: function(aAddon) {
+    if (aAddon.appDisabled) {
+      logger.warn(`System add-on ${aAddon.id} isn't compatible with the application.`);
+      return false;
+    }
+
+    if (aAddon.unpack) {
+      logger.warn(`System add-on ${aAddon.id} isn't a packed add-on.`);
+      return false;
+    }
+
+    if (!aAddon.bootstrap) {
+      logger.warn(`System add-on ${aAddon.id} isn't restartless.`);
+      return false;
+    }
+
+    if (!aAddon.multiprocessCompatible) {
+      logger.warn(`System add-on ${aAddon.id} isn't multiprocess compatible.`);
+      return false;
+    }
+
+    return true;
+  },
+
+  /**
+   * Tests whether the loaded add-on information matches what is expected.
+   */
+  isValid: function(aAddons) {
+    for (let id of Object.keys(this._addonSet.addons)) {
+      if (!aAddons.has(id)) {
+        logger.warn(`Expected add-on ${id} is missing from the system add-on location.`);
+        return false;
+      }
+
+      let addon = aAddons.get(id);
+      if (addon.version != this._addonSet.addons[id].version) {
+        logger.warn(`Expected system add-on ${id} to be version ${this._addonSet.addons[id].version} but was ${addon.version}.`);
+        return false;
+      }
+
+      if (!this.isValidAddon(addon))
+        return false;
+    }
+
+    return true;
+  },
+
+  /**
+   * Resets the add-on set so on the next startup the default set will be used.
+   */
+  resetAddonSet: function() {
+
+    if (this._addonSet) {
+      logger.info("Removing all system add-on upgrades.");
+
+      // remove everything from the pref first, if uninstall
+      // fails then at least they will not be re-activated on
+      // next restart.
+      this._saveAddonSet({ schema: 1, addons: {} });
+
+      for (let id of Object.keys(this._addonSet.addons)) {
+        AddonManager.getAddonByID(id, addon => {
+          if (addon) {
+            addon.uninstall();
+          }
+        });
+      }
+    }
+  },
+
+  /**
+   * Removes any directories not currently in use or pending use after a
+   * restart. Any errors that happen here don't really matter as we'll attempt
+   * to cleanup again next time.
+   */
+  cleanDirectories: Task.async(function*() {
+
+    // System add-ons directory does not exist
+    if (!(yield OS.File.exists(this._baseDir.path))) {
+      return;
+    }
+
+    let iterator;
+    try {
+      iterator = new OS.File.DirectoryIterator(this._baseDir.path);
+    }
+    catch (e) {
+      logger.error("Failed to clean updated system add-ons directories.", e);
+      return;
+    }
+
+    try {
+      let entries = [];
+
+      yield iterator.forEach(entry => {
+        // Skip the directory currently in use
+        if (this._directory && this._directory.path == entry.path)
+          return;
+
+        // Skip the next directory
+        if (this._nextDir && this._nextDir.path == entry.path)
+          return;
+
+        entries.push(entry);
+      });
+
+      for (let entry of entries) {
+        if (entry.isDir) {
+          yield OS.File.removeDir(entry.path, {
+            ignoreAbsent: true,
+            ignorePermissions: true,
+          });
+        }
+        else {
+          yield OS.File.remove(entry.path, {
+            ignoreAbsent: true,
+          });
+        }
+      }
+    }
+    catch (e) {
+      logger.error("Failed to clean updated system add-ons directories.", e);
+    }
+    finally {
+      iterator.close();
+    }
+  }),
+
+  /**
+   * Installs a new set of system add-ons into the location and updates the
+   * add-on set in prefs.
+   *
+   * @param {Array} aAddons - An array of addons to install.
+   */
+  installAddonSet: Task.async(function*(aAddons) {
+    // Make sure the base dir exists
+    yield OS.File.makeDir(this._baseDir.path, { ignoreExisting: true });
+
+    let addonSet = this._loadAddonSet();
+
+    // Remove any add-ons that are no longer part of the set.
+    for (let addonID of Object.keys(addonSet.addons)) {
+      if (!aAddons.includes(addonID)) {
+        AddonManager.getAddonByID(addonID, a => a.uninstall());
+      }
+    }
+
+    let newDir = this._baseDir.clone();
+
+    let uuidGen = Cc["@mozilla.org/uuid-generator;1"].
+                  getService(Ci.nsIUUIDGenerator);
+    newDir.append("blank");
+
+    while (true) {
+      newDir.leafName = uuidGen.generateUUID().toString();
+
+      try {
+        yield OS.File.makeDir(newDir.path, { ignoreExisting: false });
+        break;
+      }
+      catch (e) {
+        logger.debug("Could not create new system add-on updates dir, retrying", e);
+      }
+    }
+
+    // Record the new upgrade directory.
+    let state = { schema: 1, directory: newDir.leafName, addons: {} };
+    this._saveAddonSet(state);
+
+    this._nextDir = newDir;
+    let location = this;
+
+    let installs = [];
+    for (let addon of aAddons) {
+      let install = yield createLocalInstall(addon._sourceBundle, location);
+      installs.push(install);
+    }
+
+    let installAddon = Task.async(function*(install) {
+      // Make the new install own its temporary file.
+      install.ownsTempFile = true;
+      install.install();
+    });
+
+    let postponeAddon = Task.async(function*(install) {
+      let resumeFn;
+      if (AddonManagerPrivate.hasUpgradeListener(install.addon.id)) {
+        logger.info(`system add-on ${install.addon.id} has an upgrade listener, postponing upgrade set until restart`);
+        resumeFn = () => {
+          logger.info(`${install.addon.id} has resumed a previously postponed addon set`);
+          install.installLocation.resumeAddonSet(installs);
+        }
+      }
+      yield install.postpone(resumeFn);
+    });
+
+    let previousState;
+
+    try {
+      // All add-ons in position, create the new state and store it in prefs
+      state = { schema: 1, directory: newDir.leafName, addons: {} };
+      for (let addon of aAddons) {
+        state.addons[addon.id] = {
+          version: addon.version
+        }
+      }
+
+      previousState = this._loadAddonSet();
+      this._saveAddonSet(state);
+
+      let blockers = aAddons.filter(
+        addon => AddonManagerPrivate.hasUpgradeListener(addon.id)
+      );
+
+      if (blockers.length > 0) {
+        yield waitForAllPromises(installs.map(postponeAddon));
+      } else {
+        yield waitForAllPromises(installs.map(installAddon));
+      }
+    }
+    catch (e) {
+      // Roll back to previous upgrade set (if present) on restart.
+      if (previousState) {
+        this._saveAddonSet(previousState);
+      }
+      // Otherwise, roll back to built-in set on restart.
+      // TODO try to do these restartlessly
+      this.resetAddonSet();
+
+      try {
+        yield OS.File.removeDir(newDir.path, { ignorePermissions: true });
+      }
+      catch (e) {
+        logger.warn(`Failed to remove failed system add-on directory ${newDir.path}.`, e);
+      }
+      throw e;
+    }
+  }),
+
+ /**
+  * Resumes upgrade of a previously-delayed add-on set.
+  */
+  resumeAddonSet: Task.async(function*(installs) {
+    let resumeAddon = Task.async(function*(install) {
+      install.state = AddonManager.STATE_DOWNLOADED;
+      install.installLocation.releaseStagingDir();
+      install.install();
+    });
+
+    let addonSet = this._loadAddonSet();
+    let addonIDs = Object.keys(addonSet.addons);
+
+    let blockers = installs.filter(
+      install => AddonManagerPrivate.hasUpgradeListener(install.addon.id)
+    );
+
+    if (blockers.length > 1) {
+      logger.warn("Attempted to resume system add-on install but upgrade blockers are still present");
+    } else {
+      yield waitForAllPromises(installs.map(resumeAddon));
+    }
+  }),
+
+  /**
+   * Returns a directory that is normally on the same filesystem as the rest of
+   * the install location and can be used for temporarily storing files during
+   * safe move operations. Calling this method will delete the existing trash
+   * directory and its contents.
+   *
+   * @return an nsIFile
+   */
+  getTrashDir: function() {
+    let trashDir = this._directory.clone();
+    trashDir.append(DIR_TRASH);
+    let trashDirExists = trashDir.exists();
+    try {
+      if (trashDirExists)
+        recursiveRemove(trashDir);
+      trashDirExists = false;
+    } catch (e) {
+      logger.warn("Failed to remove trash directory", e);
+    }
+    if (!trashDirExists)
+      trashDir.create(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+
+    return trashDir;
+  },
+
+  /**
+   * Installs an add-on into the install location.
+   *
+   * @param  id
+   *         The ID of the add-on to install
+   * @param  source
+   *         The source nsIFile to install from
+   * @return an nsIFile indicating where the add-on was installed to
+   */
+  installAddon: function({id, source}) {
+    let trashDir = this.getTrashDir();
+    let transaction = new SafeInstallOperation();
+
+    // If any of these operations fails the finally block will clean up the
+    // temporary directory
+    try {
+      if (source.isFile()) {
+        flushJarCache(source);
+      }
+
+      transaction.moveUnder(source, this._directory);
+    }
+    finally {
+      // It isn't ideal if this cleanup fails but it isn't worth rolling back
+      // the install because of it.
+      try {
+        recursiveRemove(trashDir);
+      }
+      catch (e) {
+        logger.warn("Failed to remove trash directory when installing " + id, e);
+      }
+    }
+
+    let newFile = this._directory.clone();
+    newFile.append(source.leafName);
+
+    try {
+      newFile.lastModifiedTime = Date.now();
+    } catch (e)  {
+      logger.warn("failed to set lastModifiedTime on " + newFile.path, e);
+    }
+    this._IDToFileMap[id] = newFile;
+    XPIProvider._addURIMapping(id, newFile);
+
+    return newFile;
+  },
+
+  // old system add-on upgrade dirs get automatically removed
+  uninstallAddon: (aAddon) => {},
+});
+
+/**
+ * An object which identifies an install location for temporary add-ons.
+ */
+const TemporaryInstallLocation = {
+  locked: false,
+  name: KEY_APP_TEMPORARY,
+  scope: AddonManager.SCOPE_TEMPORARY,
+  getAddonLocations: () => [],
+  isLinkedAddon: () => false,
+  installAddon: () => {},
+  uninstallAddon: (aAddon) => {},
+  getStagingDir: () => {},
+}
+
+/**
+ * An object that identifies a registry install location for add-ons. The location
+ * consists of a registry key which contains string values mapping ID to the
+ * path where an add-on is installed
+ *
+ * @param  aName
+ *         The string identifier of this Install Location.
+ * @param  aRootKey
+ *         The root key (one of the ROOT_KEY_ values from nsIWindowsRegKey).
+ * @param  scope
+ *         The scope of add-ons installed in this location
+ */
+function WinRegInstallLocation(aName, aRootKey, aScope) {
+  this.locked = true;
+  this._name = aName;
+  this._rootKey = aRootKey;
+  this._scope = aScope;
+  this._IDToFileMap = {};
+
+  let path = this._appKeyPath + "\\Extensions";
+  let key = Cc["@mozilla.org/windows-registry-key;1"].
+            createInstance(Ci.nsIWindowsRegKey);
+
+  // Reading the registry may throw an exception, and that's ok.  In error
+  // cases, we just leave ourselves in the empty state.
+  try {
+    key.open(this._rootKey, path, Ci.nsIWindowsRegKey.ACCESS_READ);
+  }
+  catch (e) {
+    return;
+  }
+
+  this._readAddons(key);
+  key.close();
+}
+
+WinRegInstallLocation.prototype = {
+  _name       : "",
+  _rootKey    : null,
+  _scope      : null,
+  _IDToFileMap : null,  // mapping from ID to nsIFile
+
+  /**
+   * Retrieves the path of this Application's data key in the registry.
+   */
+  get _appKeyPath() {
+    let appVendor = Services.appinfo.vendor;
+    let appName = Services.appinfo.name;
+
+    // XXX Thunderbird doesn't specify a vendor string
+    if (AppConstants.MOZ_APP_NAME == "thunderbird" && appVendor == "")
+      appVendor = "Mozilla";
+
+    // XULRunner-based apps may intentionally not specify a vendor
+    if (appVendor != "")
+      appVendor += "\\";
+
+    return "SOFTWARE\\" + appVendor + appName;
+  },
+
+  /**
+   * Read the registry and build a mapping between ID and path for each
+   * installed add-on.
+   *
+   * @param  key
+   *         The key that contains the ID to path mapping
+   */
+  _readAddons: function(aKey) {
+    let count = aKey.valueCount;
+    for (let i = 0; i < count; ++i) {
+      let id = aKey.getValueName(i);
+
+      let file = new nsIFile(aKey.readStringValue(id));
+
+      if (!file.exists()) {
+        logger.warn("Ignoring missing add-on in " + file.path);
+        continue;
+      }
+
+      this._IDToFileMap[id] = file;
+      XPIProvider._addURIMapping(id, file);
+    }
+  },
+
+  /**
+   * Gets the name of this install location.
+   */
+  get name() {
+    return this._name;
+  },
+
+  /**
+   * Gets the scope of this install location.
+   */
+  get scope() {
+    return this._scope;
+  },
+
+  /**
+   * Gets an array of nsIFiles for add-ons installed in this location.
+   */
+  getAddonLocations: function() {
+    let locations = new Map();
+    for (let id in this._IDToFileMap) {
+      locations.set(id, this._IDToFileMap[id].clone());
+    }
+    return locations;
+  },
+
+  /**
+   * @see DirectoryInstallLocation
+   */
+  isLinkedAddon: function(aId) {
+    return true;
+  }
+};
+
+var addonTypes = [
+  new AddonManagerPrivate.AddonType("extension", URI_EXTENSION_STRINGS,
+                                    STRING_TYPE_NAME,
+                                    AddonManager.VIEW_TYPE_LIST, 4000,
+                                    AddonManager.TYPE_SUPPORTS_UNDO_RESTARTLESS_UNINSTALL),
+  new AddonManagerPrivate.AddonType("theme", URI_EXTENSION_STRINGS,
+                                    STRING_TYPE_NAME,
+                                    AddonManager.VIEW_TYPE_LIST, 5000),
+  new AddonManagerPrivate.AddonType("dictionary", URI_EXTENSION_STRINGS,
+                                    STRING_TYPE_NAME,
+                                    AddonManager.VIEW_TYPE_LIST, 7000,
+                                    AddonManager.TYPE_UI_HIDE_EMPTY | AddonManager.TYPE_SUPPORTS_UNDO_RESTARTLESS_UNINSTALL),
+  new AddonManagerPrivate.AddonType("locale", URI_EXTENSION_STRINGS,
+                                    STRING_TYPE_NAME,
+                                    AddonManager.VIEW_TYPE_LIST, 8000,
+                                    AddonManager.TYPE_UI_HIDE_EMPTY | AddonManager.TYPE_SUPPORTS_UNDO_RESTARTLESS_UNINSTALL),
+];
+
+// We only register experiments support if the application supports them.
+// Ideally, we would install an observer to watch the pref. Installing
+// an observer for this pref is not necessary here and may be buggy with
+// regards to registering this XPIProvider twice.
+if (Preferences.get("experiments.supported", false)) {
+  addonTypes.push(
+    new AddonManagerPrivate.AddonType("experiment",
+                                      URI_EXTENSION_STRINGS,
+                                      STRING_TYPE_NAME,
+                                      AddonManager.VIEW_TYPE_LIST, 11000,
+                                      AddonManager.TYPE_UI_HIDE_EMPTY | AddonManager.TYPE_SUPPORTS_UNDO_RESTARTLESS_UNINSTALL));
+}
+
+AddonManagerPrivate.registerProvider(XPIProvider, addonTypes);