Use ScopedTaskEnvironment instead of MessageLoopForUI in ui/aura/test/.

ui/views/test/views_test_helper.h

 // Copyright 2014 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.
 
 #ifndef UI_VIEWS_TEST_VIEWS_TEST_HELPER_H_
 #define UI_VIEWS_TEST_VIEWS_TEST_HELPER_H_
 
 #include "base/macros.h"
 #include "ui/gfx/native_widget_types.h"
 
-namespace base {
-class MessageLoopForUI;
-}
-
 namespace ui {
 class ContextFactory;
 class ContextFactoryPrivate;
 }
 
 namespace views {
 
 // A helper class owned by tests that performs platform specific initialization
 // required for running tests.
 class ViewsTestHelper {
  public:
   ViewsTestHelper();
   virtual ~ViewsTestHelper();
 
   // Create a platform specific instance.
   static ViewsTestHelper* Create(
-      base::MessageLoopForUI* message_loop,
       ui::ContextFactory* context_factory,
       ui::ContextFactoryPrivate* context_factory_private);
 
   // Creates objects that are needed for tests.
   virtual void SetUp();
 
   // Clean up objects that were created for tests.
   virtual void TearDown();
 
   // Returns a context view. In aura builds, this will be the
   // RootWindow. Everywhere else, NULL.
   virtual gfx::NativeWindow GetContext();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ViewsTestHelper);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_TEST_VIEWS_TEST_HELPER_H_