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

ui/views/test/views_test_helper_aura.cc

 // 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.
 
 #include "ui/views/test/views_test_helper_aura.h"
 
 #include "ui/aura/client/screen_position_client.h"
 #include "ui/aura/test/aura_test_helper.h"
 #include "ui/views/test/platform_test_helper.h"
 #include "ui/wm/core/capture_controller.h"
 #include "ui/wm/core/default_activation_client.h"
 #include "ui/wm/core/default_screen_position_client.h"
 
 namespace views {
 
 // static
 ViewsTestHelper* ViewsTestHelper::Create(
-    base::MessageLoopForUI* message_loop,
     ui::ContextFactory* context_factory,
     ui::ContextFactoryPrivate* context_factory_private) {
-  return new ViewsTestHelperAura(message_loop, context_factory,
-                                 context_factory_private);
+  return new ViewsTestHelperAura(context_factory, context_factory_private);
 }
 
 ViewsTestHelperAura::ViewsTestHelperAura(
-    base::MessageLoopForUI* message_loop,
     ui::ContextFactory* context_factory,
     ui::ContextFactoryPrivate* context_factory_private)
     : context_factory_(context_factory),
       context_factory_private_(context_factory_private) {
-  aura_test_helper_.reset(new aura::test::AuraTestHelper(message_loop));
+  aura_test_helper_.reset(new aura::test::AuraTestHelper());
 }
 
 ViewsTestHelperAura::~ViewsTestHelperAura() {
 }
 
 void ViewsTestHelperAura::EnableMusWithWindowTreeClient(
     aura::WindowTreeClient* window_tree_client) {
   aura_test_helper_->EnableMusWithWindowTreeClient(window_tree_client);
 }
 
@@ skipping 42 matching lines @@
     // single display that is intended for an ash like environment. Such a
     // configuration doesn't make sense for aura-mus-client, where it's testing
     // DesktopNativeWidgetAura.
     return nullptr;
   }
 
   return aura_test_helper_->root_window();
 }
 
 }  // namespace views