Bug 1440022: hook up remote-settings to broadcast messages r=lina

MozReview-Commit-ID: 3TYBqH94rSD

--HG--
extra : rebase_source : a529993dd94eca2f66566892839c64a4a9bcfb8f

services/settings/remote-settings.js

@@ -2,11 +2,14 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+/* global __URI__ */
+
 "use strict";
 
 var EXPORTED_SYMBOLS = [
   "RemoteSettings",
-  "jexlFilterFunc"
+  "jexlFilterFunc",
+  "remoteSettingsBroadcastHandler",
 ];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
@@ -26,6 +29,8 @@ ChromeUtils.defineModuleGetter(this, "ClientEnvironmentBase",
                                "resource://gre/modules/components-utils/ClientEnvironment.jsm");
 ChromeUtils.defineModuleGetter(this, "FilterExpressions",
                                "resource://gre/modules/components-utils/FilterExpressions.jsm");
+ChromeUtils.defineModuleGetter(this, "pushBroadcastService",
+                               "resource://gre/modules/PushBroadcastService.jsm");
 
 const PREF_SETTINGS_SERVER             = "services.settings.server";
 const PREF_SETTINGS_DEFAULT_BUCKET     = "services.settings.default_bucket";
@@ -735,7 +740,28 @@ function remoteSettingsFunction() {
     Services.obs.notifyObservers(null, "remote-settings-changes-polled");
   };
 
+
+  const broadcastID = "remote-settings/monitor_changes";
+  // When we start on a new profile there will be no ETag stored.
+  // Use an arbitrary ETag that is guaranteed not to occur.
+  // This will trigger a broadcast message but that's fine because we
+  // will check the changes on each collection and retrieve only the
+  // changes (e.g. nothing if we have a dump with the same data).
+  const currentVersion = Services.prefs.getStringPref(PREF_SETTINGS_LAST_ETAG, "\"0\"");
+  const moduleInfo = {
+    moduleURI: __URI__,
+    symbolName: "remoteSettingsBroadcastHandler",
+  };
+  pushBroadcastService.addListener(broadcastID, currentVersion,
+                                   moduleInfo);
+
   return remoteSettings;
 }
 
 var RemoteSettings = remoteSettingsFunction();
+
+var remoteSettingsBroadcastHandler = {
+  async receivedBroadcastMessage(data, broadcastID) {
+    return RemoteSettings.pollChanges();
+  }
+};