content: Cleanup class/struct forward declarations

content/browser/webui/web_ui_impl.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 CONTENT_BROWSER_WEBUI_WEB_UI_IMPL_H_
 #define CONTENT_BROWSER_WEBUI_WEB_UI_IMPL_H_
 
 #include <map>
 #include <memory>
 #include <set>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
 #include "content/public/browser/web_ui.h"
 #include "ipc/ipc_listener.h"
 
 namespace content {
 class RenderFrameHost;
-class RenderViewHost;
 
 class CONTENT_EXPORT WebUIImpl : public WebUI,
                                  public IPC::Listener,
                                  public base::SupportsWeakPtr<WebUIImpl> {
  public:
   WebUIImpl(WebContents* contents, const std::string& frame_name);
   ~WebUIImpl() override;
 
   // Called when a RenderFrame is created for a WebUI (reload after a renderer
   // crash) or when a WebUI is created for a RenderFrame (i.e. navigating from
@@ skipping 96 matching lines @@
   const std::string frame_name_;
 
   std::unique_ptr<WebUIController> controller_;
 
   DISALLOW_COPY_AND_ASSIGN(WebUIImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_WEBUI_WEB_UI_IMPL_H_