ash: Do not use MessageLoopForUI when not needed.

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/ash_switches.h"
 #include "ash/root_window_controller.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shelf/shelf_layout_manager_observer.h"
 #include "ash/shelf/shelf_widget.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/system/status_area_widget.h"
 #include "ash/system/tray/system_tray.h"
 #include "ash/system/tray/tray_background_view.h"
 #include "ash/system/tray/tray_bubble_wrapper.h"
 #include "ash/system/tray/tray_constants.h"
 #include "ash/system/tray/tray_utils.h"
 #include "ash/system/web_notification/ash_popup_alignment_delegate.h"
 #include "base/auto_reset.h"
 #include "base/i18n/number_formatting.h"
 #include "base/i18n/rtl.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/thread_task_runner_handle.h"
 #include "grit/ash_strings.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/gfx/screen.h"
 #include "ui/message_center/message_center_style.h"
 #include "ui/message_center/message_center_tray_delegate.h"
 #include "ui/message_center/views/message_bubble_base.h"
 #include "ui/message_center/views/message_center_bubble.h"
 #include "ui/message_center/views/message_popup_collection.h"
@@ skipping 402 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;
-  base::MessageLoop::current()->PostTask(
+  base::ThreadTaskRunnerHandle::Get()->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 35 matching lines @@
 
 message_center::MessageCenterBubble*
 WebNotificationTray::GetMessageCenterBubbleForTest() {
   if (!message_center_bubble())
     return NULL;
   return static_cast<message_center::MessageCenterBubble*>(
       message_center_bubble()->bubble());
 }
 
 }  // namespace ash