Use base::MessageLoop in more files.

ash/system/web_notification/web_notification_tray.cc

 // Copyright (c) 2012 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 "ash/system/web_notification/web_notification_tray.h"
 
 #include "ash/root_window_controller.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
@@ skipping 446 matching lines @@
                                         const ui::Event& event) {
   DCHECK_EQ(button_, sender);
   PerformAction(event);
 }
 
 void WebNotificationTray::OnMessageCenterTrayChanged() {
   // Do not update the tray contents directly. Multiple change events can happen
   // consecutively, and calling Update in the middle of those events will show
   // intermediate unread counts for a moment.
   should_update_tray_content_ = true;
-  MessageLoop::current()->PostTask(
+  base::MessageLoop::current()->PostTask(
       FROM_HERE,
       base::Bind(&WebNotificationTray::UpdateTrayContent, AsWeakPtr()));
 }
 
 void WebNotificationTray::UpdateTrayContent() {
   if (!should_update_tray_content_)
     return;
   should_update_tray_content_ = false;
 
   message_center::MessageCenter* message_center =
@@ skipping 38 matching lines @@
 
 message_center::MessagePopupBubble*
 WebNotificationTray::GetPopupBubbleForTest() {
   if (!popup_bubble())
     return NULL;
   return static_cast<message_center::MessagePopupBubble*>(
       popup_bubble()->bubble());
 }
 
 }  // namespace ash