Use ScopedTaskEnvironment instead of MessageLoop in service_manager::test::ServiceTest.

services/ui/ws/window_manager_client_unittest.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 <stddef.h>
 #include <stdint.h>
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/macros.h"
@@ skipping 345 matching lines @@
   };
 
   void EmbedCallbackImpl(bool result) {
     embed_details_->callback_run = true;
     embed_details_->embed_result = result;
     if (embed_details_->waiting &&
         (!result || embed_details_->result->window_tree_client))
       EXPECT_TRUE(WindowServerTestBase::QuitRunLoop());
   }
 
-  // mojo::test::ServiceTest::
-  std::unique_ptr<base::MessageLoop> CreateMessageLoop() override {
-    // The window server is expected to run with a TYPE_UI message loop.
-    return base::MakeUnique<base::MessageLoop>(base::MessageLoop::TYPE_UI);
-  }
-
   std::unique_ptr<EmbedDetails> embed_details_;
 
   std::unique_ptr<ClientAreaChange> client_area_change_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowServerTest);
 };
 
 TEST_F(WindowServerTest, RootWindow) {
   ASSERT_NE(nullptr, window_manager());
   EXPECT_EQ(1u, window_manager()->GetRoots().size());
@@ skipping 398 matching lines @@
   ASSERT_EQ(1u, top_level_in_wm->children().size());
   aura::Window* second_client_child_in_wm = top_level_in_wm->children()[0];
   ASSERT_EQ(1u, second_client_child_in_wm->children().size());
   aura::Window* transient_in_wm = second_client_child_in_wm->children()[0];
   ASSERT_EQ(second_client_child_in_wm,
             transient_window_client->GetTransientParent(transient_in_wm));
 }
 
 }  // namespace ws
 }  // namespace ui