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

ui/views/test/views_test_helper_mac.mm

 // 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_mac.h"
 
 #import <Cocoa/Cocoa.h>
 
 #import "base/mac/scoped_nsautorelease_pool.h"
 #include "ui/base/test/scoped_fake_full_keyboard_access.h"
 #include "ui/base/test/scoped_fake_nswindow_focus.h"
 #include "ui/base/test/scoped_fake_nswindow_fullscreen.h"
 #include "ui/base/test/ui_controls.h"
 #include "ui/compositor/scoped_animation_duration_scale_mode.h"
 #include "ui/views/test/event_generator_delegate_mac.h"
 #include "ui/views/widget/widget.h"
 
 namespace views {
 
 // static
 ViewsTestHelper* ViewsTestHelper::Create(
-    base::MessageLoopForUI* message_loop,
     ui::ContextFactory* context_factory,
     ui::ContextFactoryPrivate* context_factory_private) {
   return new ViewsTestHelperMac;
 }
 
 ViewsTestHelperMac::ViewsTestHelperMac()
     : zero_duration_mode_(new ui::ScopedAnimationDurationScaleMode(
           ui::ScopedAnimationDurationScaleMode::ZERO_DURATION)) {
   test::InitializeMacEventGeneratorDelegate();
 
@@ skipping 26 matching lines @@
   // this is handled automatically by views::Widget::CloseAllSecondaryWidgets().
   // Unit tests on Aura may create Widgets owned by a RootWindow that gets torn
   // down, but on Mac we need to be more explicit.
   base::mac::ScopedNSAutoreleasePool pool;  // Ensure the NSArray is released.
   NSArray* native_windows = [NSApp windows];
   for (NSWindow* window : native_windows)
     DCHECK(!Widget::GetWidgetForNativeWindow(window)) << "Widget not closed.";
 }
 
 }  // namespace views