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diff --git a/webbrowser/components/downloads/DownloadsStartup.js b/webbrowser/components/downloads/DownloadsStartup.js
new file mode 100644
index 0000000..e1dd207
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+++ b/webbrowser/components/downloads/DownloadsStartup.js
@@ -0,0 +1,278 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This component listens to notifications for startup, shutdown and session
+ * restore, controlling which downloads should be loaded from the database.
+ *
+ * To avoid affecting startup performance, this component monitors the current
+ * session restore state, but defers the actual downloads data manipulation
+ * until the Download Manager service is loaded.
+ */
+
+"use strict";
+
+////////////////////////////////////////////////////////////////////////////////
+//// Globals
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+const Cr = Components.results;
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadsCommon",
+                                  "resource:///modules/DownloadsCommon.jsm");
+XPCOMUtils.defineLazyServiceGetter(this, "gSessionStartup",
+                                   "@mozilla.org/browser/sessionstartup;1",
+                                   "nsISessionStartup");
+
+const kObservedTopics = [
+  "sessionstore-windows-restored",
+  "sessionstore-browser-state-restored",
+  "download-manager-initialized",
+  "download-manager-change-retention",
+  "last-pb-context-exited",
+  "browser-lastwindow-close-granted",
+  "quit-application",
+  "profile-change-teardown",
+];
+
+/**
+ * CID of our implementation of nsIDownloadManagerUI.
+ */
+const kDownloadsUICid = Components.ID("{4d99321e-d156-455b-81f7-e7aa2308134f}");
+
+/**
+ * Contract ID of the service implementing nsIDownloadManagerUI.
+ */
+const kDownloadsUIContractId = "@mozilla.org/download-manager-ui;1";
+
+/**
+ * CID of the JavaScript implementation of nsITransfer.
+ */
+const kTransferCid = Components.ID("{1b4c85df-cbdd-4bb6-b04e-613caece083c}");
+
+/**
+ * Contract ID of the service implementing nsITransfer.
+ */
+const kTransferContractId = "@mozilla.org/transfer;1";
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsStartup
+
+function DownloadsStartup() { }
+
+DownloadsStartup.prototype = {
+  classID: Components.ID("{49507fe5-2cee-4824-b6a3-e999150ce9b8}"),
+
+  _xpcom_factory: XPCOMUtils.generateSingletonFactory(DownloadsStartup),
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// nsISupports
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver,
+                                         Ci.nsISupportsWeakReference]),
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// nsIObserver
+
+  observe: function DS_observe(aSubject, aTopic, aData)
+  {
+    switch (aTopic) {
+      case "profile-after-change":
+        // Override Toolkit's nsIDownloadManagerUI implementation with our own.
+        // This must be done at application startup and not in the manifest to
+        // ensure that our implementation overrides the original one.
+        Components.manager.QueryInterface(Ci.nsIComponentRegistrar)
+                          .registerFactory(kDownloadsUICid, "",
+                                           kDownloadsUIContractId, null);
+
+        Components.manager.QueryInterface(Ci.nsIComponentRegistrar)
+                          .registerFactory(kTransferCid, "",
+                                           kTransferContractId, null);
+        break;
+
+      case "sessionstore-windows-restored":
+      case "sessionstore-browser-state-restored":
+        // Unless there is no saved session, there is a chance that we are
+        // starting up after a restart or a crash.  We should check the disk
+        // database to see if there are completed downloads to recover and show
+        // in the panel, in addition to in-progress downloads.
+        if (gSessionStartup.sessionType != Ci.nsISessionStartup.NO_SESSION) {
+          this._restoringSession = true;
+        }
+        this._ensureDataLoaded();
+        break;
+
+      case "download-manager-initialized":
+        // Don't initialize the JavaScript data and user interface layer if we
+        // are initializing the Download Manager service during shutdown.
+        if (this._shuttingDown) {
+          break;
+        }
+
+        // Start receiving events for active and new downloads before we return
+        // from this observer function.  We can't defer the execution of this
+        // step, to ensure that we don't lose events raised in the meantime.
+        DownloadsCommon.initializeAllDataLinks(
+                        aSubject.QueryInterface(Ci.nsIDownloadManager));
+
+        this._downloadsServiceInitialized = true;
+
+        // Since this notification is generated during the getService call and
+        // we need to get the Download Manager service ourselves, we must post
+        // the handler on the event queue to be executed later.
+        Services.tm.mainThread.dispatch(this._ensureDataLoaded.bind(this),
+                                        Ci.nsIThread.DISPATCH_NORMAL);
+        break;
+
+      case "download-manager-change-retention":
+        // If we're using the Downloads Panel, we override the retention
+        // preference to always retain downloads on completion.
+        if (!DownloadsCommon.useToolkitUI) {
+          aSubject.QueryInterface(Ci.nsISupportsPRInt32).data = 2;
+        }
+        break;
+
+      case "browser-lastwindow-close-granted":
+        // When using the panel interface, downloads that are already completed
+        // should be removed when the last full browser window is closed.  This
+        // event is invoked only if the application is not shutting down yet.
+        // If the Download Manager service is not initialized, we don't want to
+        // initialize it just to clean up completed downloads, because they can
+        // be present only in case there was a browser crash or restart.
+        if (this._downloadsServiceInitialized &&
+            !DownloadsCommon.useToolkitUI) {
+          Services.downloads.cleanUp();
+        }
+        break;
+
+      case "last-pb-context-exited":
+        // Similar to the above notification, but for private downloads.
+        if (this._downloadsServiceInitialized &&
+            !DownloadsCommon.useToolkitUI) {
+          Services.downloads.cleanUpPrivate();
+        }
+        break;
+
+      case "quit-application":
+        // When the application is shutting down, we must free all resources in
+        // addition to cleaning up completed downloads.  If the Download Manager
+        // service is not initialized, we don't want to initialize it just to
+        // clean up completed downloads, because they can be present only in
+        // case there was a browser crash or restart.
+        this._shuttingDown = true;
+        if (!this._downloadsServiceInitialized) {
+          break;
+        }
+
+        DownloadsCommon.terminateAllDataLinks();
+
+        // When using the panel interface, downloads that are already completed
+        // should be removed when quitting the application.
+        if (!DownloadsCommon.useToolkitUI && aData != "restart") {
+          this._cleanupOnShutdown = true;
+        }
+        break;
+
+      case "profile-change-teardown":
+        // If we need to clean up, we must do it synchronously after all the
+        // "quit-application" listeners are invoked, so that the Download
+        // Manager service has a chance to pause or cancel in-progress downloads
+        // before we remove completed downloads from the list.  Note that, since
+        // "quit-application" was invoked, we've already exited Private Browsing
+        // Mode, thus we are always working on the disk database.
+        if (this._cleanupOnShutdown) {
+          Services.downloads.cleanUp();
+        }
+
+        if (!DownloadsCommon.useToolkitUI) {
+          // If we got this far, that means that we finished our first session
+          // with the Downloads Panel without crashing. This means that we don't
+          // have to force displaying only active downloads on the next startup
+          // now.
+          this._firstSessionCompleted = true;
+        }
+        break;
+    }
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Private
+
+  /**
+   * Indicates whether we're restoring a previous session. This is used by
+   * _recoverAllDownloads to determine whether or not we should load and
+   * display all downloads data, or restrict it to only the active downloads.
+   */
+  _restoringSession: false,
+
+  /**
+   * Indicates whether the Download Manager service has been initialized.  This
+   * flag is required because we want to avoid accessing the service immediately
+   * at browser startup.  The service will start when the user first requests a
+   * download, or some time after browser startup.
+   */
+  _downloadsServiceInitialized: false,
+
+  /**
+   * True while we are processing the "quit-application" event, and later.
+   */
+  _shuttingDown: false,
+
+  /**
+   * True during shutdown if we need to remove completed downloads.
+   */
+  _cleanupOnShutdown: false,
+
+  /**
+   * True if we should display all downloads, as opposed to just active
+   * downloads. We decide to display all downloads if we're restoring a session,
+   * or if we're using the Downloads Panel anytime after the first session with
+   * it has completed.
+   */
+  get _recoverAllDownloads() {
+    return this._restoringSession ||
+           (!DownloadsCommon.useToolkitUI && this._firstSessionCompleted);
+  },
+
+  /**
+   * True if we've ever completed a session with the Downloads Panel enabled.
+   */
+  get _firstSessionCompleted() {
+    return Services.prefs
+                   .getBoolPref("browser.download.panel.firstSessionCompleted");
+  },
+
+  set _firstSessionCompleted(aValue) {
+    Services.prefs.setBoolPref("browser.download.panel.firstSessionCompleted",
+                               aValue);
+    return aValue;
+  },
+
+  /**
+   * Ensures that persistent download data is reloaded at the appropriate time.
+   */
+  _ensureDataLoaded: function DS_ensureDataLoaded()
+  {
+    if (!this._downloadsServiceInitialized) {
+      return;
+    }
+
+    // If the previous session has been already restored, then we ensure that
+    // all the downloads are loaded.  Otherwise, we only ensure that the active
+    // downloads from the previous session are loaded.
+    DownloadsCommon.ensureAllPersistentDataLoaded(!this._recoverAllDownloads);
+  }
+};
+
+////////////////////////////////////////////////////////////////////////////////
+//// Module
+
+this.NSGetFactory = XPCOMUtils.generateNSGetFactory([DownloadsStartup]);