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

ui/views/test/views_test_helper_aura.h

Index: ui/views/test/views_test_helper_aura.h
diff --git a/ui/views/test/views_test_helper_aura.h b/ui/views/test/views_test_helper_aura.h
index 158c3ac9786c29361df9c9216ed90d362d8e5e22..f0edfc6e74a73f94fc0418e5010923219bd210ab 100644
--- a/ui/views/test/views_test_helper_aura.h
+++ b/ui/views/test/views_test_helper_aura.h
@@ -22,16 +22,11 @@ class AuraTestHelper;
 }
 }
 
-namespace base {
-class MessageLoopForUI;
-}
-
 namespace views {
 
 class ViewsTestHelperAura : public ViewsTestHelper {
  public:
-  ViewsTestHelperAura(base::MessageLoopForUI* message_loop,
-                      ui::ContextFactory* context_factory,
+  ViewsTestHelperAura(ui::ContextFactory* context_factory,
                       ui::ContextFactoryPrivate* context_factory_private);
   ~ViewsTestHelperAura() override;