Use ScopedTaskEnvironment instead of MessageLoop in components unit tests.

components/history/core/browser/web_history_service_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 "components/history/core/browser/web_history_service.h"
 
 #include <memory>
 
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/signin/core/browser/account_tracker_service.h"
 #include "components/signin/core/browser/fake_profile_oauth2_token_service.h"
 #include "components/signin/core/browser/fake_signin_manager.h"
 #include "components/signin/core/browser/test_signin_client.h"
 #include "net/http/http_status_code.h"
 #include "net/url_request/url_request_test_util.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 201 matching lines @@
     base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
                                                   run_loop.QuitClosure());
     run_loop.Run();
   }
 
   TestingWebHistoryService* web_history_service() {
     return &web_history_service_;
   }
 
  private:
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   FakeProfileOAuth2TokenService token_service_;
   AccountTrackerService account_tracker_;
   TestSigninClient signin_client_;
   FakeSigninManagerBase signin_manager_;
   scoped_refptr<net::URLRequestContextGetter> url_request_context_;
   TestingWebHistoryService web_history_service_;
 
   DISALLOW_COPY_AND_ASSIGN(WebHistoryServiceTest);
 };
 
@@ skipping 130 matching lines @@
   std::unique_ptr<base::DictionaryValue> response_value5;
   // ReadResponse deletes the request
   response_value5 = TestingWebHistoryService::ReadResponse(request5.get());
   enabled_value = true;
   EXPECT_FALSE(response_value5->GetBoolean("history_recording_enabled",
                                            &enabled_value));
   EXPECT_TRUE(enabled_value);
 }
 
 }  // namespace history