Bug 1184825 - treat FxAccountsWebChannel as a singleton to avoid creating one per window. r=stomlinson

browser/base/content/browser-fxaccounts.js

@@ -110,14 +110,7 @@ let gFxAccounts = {
     // notified of fxa-migration:state-changed in response if necessary.
     Services.obs.notifyObservers(null, "fxa-migration:state-request", null);
 
-    let contentUri = Services.urlFormatter.formatURLPref("identity.fxaccounts.remote.webchannel.uri");
-    // The FxAccountsWebChannel listens for events and updates
-    // the state machine accordingly.
-    let fxAccountsWebChannel = new FxAccountsWebChannel({
-      content_uri: contentUri,
-      channel_id: this.FxAccountsCommon.WEBCHANNEL_ID
-    });
-
+    EnsureFxAccountsWebChannel();
     this._initialized = true;
 
     this.updateUI();
@@ -482,5 +475,5 @@ XPCOMUtils.defineLazyGetter(gFxAccounts, "FxAccountsCommon", function () {
 XPCOMUtils.defineLazyModuleGetter(gFxAccounts, "fxaMigrator",
   "resource://services-sync/FxaMigrator.jsm");
 
-XPCOMUtils.defineLazyModuleGetter(this, "FxAccountsWebChannel",
+XPCOMUtils.defineLazyModuleGetter(this, "EnsureFxAccountsWebChannel",
   "resource://gre/modules/FxAccountsWebChannel.jsm");

browser/base/content/test/general/browser_fxa_web_channel.js

@@ -12,8 +12,9 @@ XPCOMUtils.defineLazyGetter(this, "FxAccountsCommon", function () {
 XPCOMUtils.defineLazyModuleGetter(this, "WebChannel",
                                   "resource://gre/modules/WebChannel.jsm");
 
-XPCOMUtils.defineLazyModuleGetter(this, "FxAccountsWebChannel",
-  "resource://gre/modules/FxAccountsWebChannel.jsm");
+// FxAccountsWebChannel isn't explicitly exported by FxAccountsWebChannel.jsm
+// but we can get it here via a backstage pass.
+let {FxAccountsWebChannel} = Components.utils.import("resource://gre/modules/FxAccountsWebChannel.jsm", {});
 
 const TEST_HTTP_PATH = "http://example.com";
 const TEST_BASE_URL = TEST_HTTP_PATH + "/browser/browser/base/content/test/general/browser_fxa_web_channel.html";

services/fxaccounts/FxAccountsWebChannel.jsm

@@ -9,7 +9,7 @@
  * about account state changes.
  */
 
-this.EXPORTED_SYMBOLS = ["FxAccountsWebChannel"];
+this.EXPORTED_SYMBOLS = ["EnsureFxAccountsWebChannel"];
 
 const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
 
@@ -311,3 +311,21 @@ this.FxAccountsWebChannelHelpers.prototype = {
     return pressed === 0; // 0 is the "continue" button
   }
 };
+
+let singleton;
+// The entry-point for this module, which ensures only one of our channels is
+// ever created - we require this because the WebChannel is global in scope
+// (eg, it uses the observer service to tell interested parties of interesting
+// things) and allowing multiple channels would cause such notifications to be
+// sent multiple times.
+this.EnsureFxAccountsWebChannel = function() {
+  if (!singleton) {
+    let contentUri = Services.urlFormatter.formatURLPref("identity.fxaccounts.remote.webchannel.uri");
+    // The FxAccountsWebChannel listens for events and updates
+    // the state machine accordingly.
+    singleton = new this.FxAccountsWebChannel({
+      content_uri: contentUri,
+      channel_id: WEBCHANNEL_ID,
+    });
+  }
+}