Fix some issues with extension messaging:

chrome/renderer/resources/event_bindings.js

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // -----------------------------------------------------------------------------
 // NOTE: If you change this file you need to touch renderer_resources.grd to
 // have your change take effect.
 // -----------------------------------------------------------------------------
 
 var chrome = chrome || {};
@@ skipping 41 matching lines @@
   };
 
   // Dispatches a named event with the given arguments, supplied as an array.
   chromeHidden.Event.dispatch = function(name, args) {
     if (attachedNamedEvents[name]) {
       attachedNamedEvents[name].dispatch.apply(
           attachedNamedEvents[name], args);
     }
   };
 
+  // Test if a named event has any listeners.
+  chromeHidden.Event.hasListener = function(name) {
+    return (attachedNamedEvents[name] &&
+            attachedNamedEvents[name].listeners_.length > 0);
+  }
+
   // Registers a callback to be called when this event is dispatched.
   chrome.Event.prototype.addListener = function(cb) {
     this.listeners_.push(cb);
     if (this.listeners_.length == 1) {
       this.attach_();
     }
   };
 
   // Unregisters a callback.
   chrome.Event.prototype.removeListener = function(cb) {
@@ skipping 103 matching lines @@
     var sargs = JSON.stringify(args);
     var requestId = GetNextRequestId();
     var hasCallback = false;
     if (callback) {
       hasCallback = true;
       callbacks[requestId] = callback;
     }
     request(sargs, requestId, hasCallback);
   }
 
-  // Special unload event: we don't use the DOM unload because that slows
-  // down tab shutdown.  On the other hand, this might not always fire, since
-  // Chrome will terminate renderers on shutdown (SuddenTermination).
+  // Special load events: we don't use the DOM unload because that slows
+  // down tab shutdown.  On the other hand, onUnload might not always fire,
+  // since Chrome will terminate renderers on shutdown (SuddenTermination).
+  chromeHidden.onLoad = new chrome.Event();
   chromeHidden.onUnload = new chrome.Event();
 
+  chromeHidden.dispatchOnLoad = function(extensionId) {
+    chromeHidden.onLoad.dispatch(extensionId);
+  }
+
   chromeHidden.dispatchOnUnload = function() {
     chromeHidden.onUnload.dispatch();
     for (var i in allAttachedEvents)
       allAttachedEvents[i].detach_();
   }
 })();