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

ui/aura/test/aura_test_base.cc

 // Copyright (c) 2012 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/aura/test/aura_test_base.h"
 
+#include "base/memory/ptr_util.h"
 #include "ui/aura/client/window_parenting_client.h"
 #include "ui/aura/mus/property_utils.h"
 #include "ui/aura/mus/window_tree_client.h"
 #include "ui/aura/mus/window_tree_host_mus.h"
 #include "ui/aura/test/test_window_delegate.h"
 #include "ui/aura/window.h"
 #include "ui/base/ime/input_method_initializer.h"
 #include "ui/base/material_design/material_design_controller.h"
 #include "ui/base/test/material_design_controller_test_api.h"
 #include "ui/compositor/test/context_factories_for_test.h"
 #include "ui/events/event_dispatcher.h"
 #include "ui/events/event_sink.h"
 #include "ui/events/gesture_detection/gesture_configuration.h"
 
 namespace aura {
 namespace test {
 
 AuraTestBase::AuraTestBase()
-    : window_manager_delegate_(this), window_tree_client_delegate_(this) {}
+    : scoped_task_environment_(
+          base::test::ScopedTaskEnvironment::MainThreadType::UI),
+      window_manager_delegate_(this),
+      window_tree_client_delegate_(this) {}
 
 AuraTestBase::~AuraTestBase() {
   CHECK(setup_called_)
       << "You have overridden SetUp but never called super class's SetUp";
   CHECK(teardown_called_)
       << "You have overridden TearDown but never called super class's TearDown";
 }
 
 void AuraTestBase::SetUp() {
   setup_called_ = true;
@@ skipping 36 matching lines @@
   gesture_config->set_velocity_tracker_strategy(
       ui::VelocityTracker::Strategy::LSQ2_RESTRICTED);
 
   // The ContextFactory must exist before any Compositors are created.
   bool enable_pixel_output = false;
   ui::ContextFactory* context_factory = nullptr;
   ui::ContextFactoryPrivate* context_factory_private = nullptr;
   ui::InitializeContextFactoryForTests(enable_pixel_output, &context_factory,
                                        &context_factory_private);
 
-  helper_.reset(new AuraTestHelper(&message_loop_));
+  helper_ = base::MakeUnique<AuraTestHelper>();
   if (use_mus_) {
     helper_->EnableMusWithTestWindowTree(window_tree_client_delegate_,
                                          window_manager_delegate_);
   }
   helper_->SetUp(context_factory, context_factory_private);
 }
 
 void AuraTestBase::TearDown() {
   teardown_called_ = true;
 
@@ skipping 159 matching lines @@
 
 AuraTestBaseMus::~AuraTestBaseMus() {}
 
 void AuraTestBaseMus::SetUp() {
   ConfigureBackend(test::BackendType::MUS);
   AuraTestBase::SetUp();
 }
 
 }  // namespace test
 }  // namespace aura