ui: Cleanup class/struct forward declarations

ui/views/test/webview_test_helper.h

 // 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.
 
 #ifndef UI_VIEWS_TEST_WEB_VIEW_TEST_HELPER_H_
 #define UI_VIEWS_TEST_WEB_VIEW_TEST_HELPER_H_
 
 #include <memory>
 
 #include "base/macros.h"
 
-namespace base {
-class MessageLoopForUI;
-}
-
 namespace content {
 class TestContentClientInitializer;
 }  // namespace content
 
 namespace views {
 
 class WebViewTestHelper {
  public:
   WebViewTestHelper();
   virtual ~WebViewTestHelper();
 
  private:
   std::unique_ptr<content::TestContentClientInitializer>
       test_content_client_initializer_;
 
   DISALLOW_COPY_AND_ASSIGN(WebViewTestHelper);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_TEST_WEB_VIEW_TEST_HELPER_H_