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

ui/views/test/views_test_helper.h

Index: ui/views/test/views_test_helper.h
diff --git a/ui/views/test/views_test_helper.h b/ui/views/test/views_test_helper.h
index 787648dc04595fcee8c078d6a170148e9c9718db..46fc0eb33cadb301689db1d698cba4901b2ed7c4 100644
--- a/ui/views/test/views_test_helper.h
+++ b/ui/views/test/views_test_helper.h
@@ -8,10 +8,6 @@
 #include "base/macros.h"
 #include "ui/gfx/native_widget_types.h"
 
-namespace base {
-class MessageLoopForUI;
-}
-
 namespace ui {
 class ContextFactory;
 class ContextFactoryPrivate;
@@ -28,7 +24,6 @@ class ViewsTestHelper {
 
   // Create a platform specific instance.
   static ViewsTestHelper* Create(
-      base::MessageLoopForUI* message_loop,
       ui::ContextFactory* context_factory,
       ui::ContextFactoryPrivate* context_factory_private);