ash: Do not use MessageLoopForUI when not needed.

ash/system/chromeos/brightness/tray_brightness.cc

 // Copyright 2013 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/chromeos/brightness/tray_brightness.h"
 
 #include <algorithm>
 
 #include "ash/accelerators/accelerator_controller.h"
 #include "ash/ash_constants.h"
 #include "ash/metrics/user_metrics_recorder.h"
 #include "ash/shell.h"
 #include "ash/shell_observer.h"
 #include "ash/system/brightness_control_delegate.h"
 #include "ash/system/tray/fixed_sized_image_view.h"
 #include "ash/system/tray/system_tray_delegate.h"
 #include "ash/system/tray/system_tray_notifier.h"
 #include "ash/system/tray/tray_constants.h"
 #include "ash/wm/maximize_mode/maximize_mode_controller.h"
 #include "base/bind.h"
-#include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/thread_task_runner_handle.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/power_manager_client.h"
 #include "grit/ash_resources.h"
 #include "grit/ash_strings.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/image/image.h"
 #include "ui/views/controls/button/image_button.h"
 #include "ui/views/controls/image_view.h"
 #include "ui/views/controls/label.h"
@@ skipping 140 matching lines @@
 }  // namespace tray
 
 TrayBrightness::TrayBrightness(SystemTray* system_tray)
     : SystemTrayItem(system_tray),
       brightness_view_(NULL),
       current_percent_(100.0),
       got_current_percent_(false),
       weak_ptr_factory_(this) {
   // Post a task to get the initial brightness; the BrightnessControlDelegate
   // isn't created yet.
-  base::MessageLoopForUI::current()->PostTask(
-      FROM_HERE,
-      base::Bind(&TrayBrightness::GetInitialBrightness,
-                 weak_ptr_factory_.GetWeakPtr()));
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE, base::Bind(&TrayBrightness::GetInitialBrightness,
+                            weak_ptr_factory_.GetWeakPtr()));
   chromeos::DBusThreadManager::Get()->GetPowerManagerClient()->
       AddObserver(this);
 }
 
 TrayBrightness::~TrayBrightness() {
   chromeos::DBusThreadManager::Get()->GetPowerManagerClient()->
       RemoveObserver(this);
 }
 
 void TrayBrightness::GetInitialBrightness() {
@@ skipping 79 matching lines @@
   if (!gfx::Display::HasInternalDisplay())
     return;
 
   if (brightness_view_)
     SetDetailedViewCloseDelay(kTrayPopupAutoCloseDelayInSeconds);
   else
     PopupDetailedView(kTrayPopupAutoCloseDelayInSeconds, false);
 }
 
 }  // namespace ash