Adds the source ImageLoadingTracker to OnImageLoaded. I need this in a

chrome/browser/gtk/browser_actions_toolbar_gtk.cc

 // Copyright (c) 2010 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.
 
 #include "chrome/browser/gtk/browser_actions_toolbar_gtk.h"
 
 #include <vector>
 
 #include "app/gfx/canvas_paint.h"
 #include "chrome/browser/browser.h"
@@ skipping 113 matching lines @@
   void Observe(NotificationType type,
                const NotificationSource& source,
                const NotificationDetails& details) {
     if (type == NotificationType::EXTENSION_BROWSER_ACTION_UPDATED)
       UpdateState();
     else
       NOTREACHED();
   }
 
   // ImageLoadingTracker::Observer implementation.
-  void OnImageLoaded(SkBitmap* image, size_t index) {
+  void OnImageLoaded(ImageLoadingTracker* source, SkBitmap* image,
+                     size_t index) {
     if (image) {
       default_skbitmap_ = *image;
       default_icon_ = gfx::GdkPixbufFromSkBitmap(image);
     }
     tracker_ = NULL;  // The tracker object will delete itself when we return.
     UpdateState();
   }
 
   // Updates the button based on the latest state from the associated
   // browser action.
@@ skipping 596 matching lines @@
 
     // TODO(estade): set the menu item's tooltip.
   }
 
   gtk_chrome_button_set_paint_state(GTK_CHROME_BUTTON(overflow),
                                     GTK_STATE_ACTIVE);
   overflow_menu_->PopupAsFromKeyEvent(overflow);
 
   return FALSE;
 }