Update browser actions api to be like new design doc.

chrome/browser/gtk/browser_actions_toolbar_gtk.cc

 // 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.
 
 #include "chrome/browser/gtk/browser_actions_toolbar_gtk.h"
 
 #include <gtk/gtk.h>
 #include <vector>
 
 #include "app/gfx/gtk_util.h"
@@ skipping 75 matching lines @@
 
   // NotificationObserver implementation.
   void Observe(NotificationType type,
                const NotificationSource& source,
                const NotificationDetails& details) {
     OnStateUpdated();
   }
 
   // ImageLoadingTracker::Observer implementation.
   void OnImageLoaded(SkBitmap* image, size_t index) {
-    browser_action_icons_[index] = gfx::GdkPixbufFromSkBitmap(image);
+    if (image) {
+      browser_action_icons_[index] = gfx::GdkPixbufFromSkBitmap(image);
+    } else {
+      SkBitmap empty;
+      browser_action_icons_[index] = gfx::GdkPixbufFromSkBitmap(&empty);
+    }
+
     OnStateUpdated();
   }
 
  private:
   // The Browser that executes a command when the button is pressed.
   Browser* browser_;
 
   // The extension that contains this browser action.
   Extension* extension_;
 
@@ skipping 81 matching lines @@
   if (extension_button_map_.erase(extension->id()))
     UpdateVisibility();
 }
 
 void BrowserActionsToolbarGtk::UpdateVisibility() {
   if (button_count() == 0)
     gtk_widget_hide(widget());
   else
     gtk_widget_show(widget());
 }