Backout 3c0d710561bf (bug 927363) due to causing bug 930296.

dom/messages/SystemMessageManager.js

@@ -136,7 +136,6 @@ SystemMessageManager.prototype = {
     dispatchers[aType] = { handler: aHandler, messages: [], isHandling: false };
 
     // Ask for the list of currently pending messages.
-    this.addMessageListeners("SystemMessageManager:GetPendingMessages:Return");
     cpmm.sendAsyncMessage("SystemMessageManager:GetPendingMessages",
                           { type: aType,
                             uri: this._uri,
@@ -215,8 +214,6 @@ SystemMessageManager.prototype = {
                               manifest: this._manifest,
                               uri: this._uri,
                               msgID: msg.msgID });
-    } else if (aMessage.name == "SystemMessageManager:GetPendingMessages:Return") {
-      this.removeMessageListeners(aMessage.name);
     }
 
     let messages = (aMessage.name == "SystemMessageManager:Message")
@@ -251,7 +248,8 @@ SystemMessageManager.prototype = {
   // nsIDOMGlobalPropertyInitializer implementation.
   init: function sysMessMgr_init(aWindow) {
     debug("init");
-    this.initDOMRequestHelper(aWindow, ["SystemMessageManager:Message"]);
+    this.initDOMRequestHelper(aWindow, ["SystemMessageManager:Message",
+                              "SystemMessageManager:GetPendingMessages:Return"]);
 
     let principal = aWindow.document.nodePrincipal;
     this._isInBrowserElement = principal.isInBrowserElement;