content: Cleanup class/struct forward declarations

content/shell/renderer/layout_test/layout_test_render_thread_observer.h

 // Copyright (c) 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.
 
 #ifndef CONTENT_SHELL_RENDERER_LAYOUT_TEST_LAYOUT_TEST_RENDER_THREAD_OBSERVER_H_
 #define CONTENT_SHELL_RENDERER_LAYOUT_TEST_LAYOUT_TEST_RENDER_THREAD_OBSERVER_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "content/public/renderer/render_thread_observer.h"
 #include "ipc/ipc_platform_file.h"
 
 namespace base {
 class DictionaryValue;
 }
 
-namespace blink {
-class WebFrame;
-}
-
 namespace test_runner {
 class WebTestInterfaces;
 }
 
 namespace content {
 
 class LayoutTestRenderThreadObserver : public RenderThreadObserver {
  public:
   static LayoutTestRenderThreadObserver* GetInstance();
 
@@ skipping 18 matching lines @@
   std::unique_ptr<test_runner::WebTestInterfaces> test_interfaces_;
 
   base::FilePath webkit_source_dir_;
 
   DISALLOW_COPY_AND_ASSIGN(LayoutTestRenderThreadObserver);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_SHELL_RENDERER_LAYOUT_TEST_LAYOUT_TEST_RENDER_THREAD_OBSERVER_H_