content: Cleanup class/struct forward declarations

content/browser/frame_host/frame_tree.h

 // Copyright 2013 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_FRAME_HOST_FRAME_TREE_H_
 #define CONTENT_BROWSER_FRAME_HOST_FRAME_TREE_H_
 
 #include <stdint.h>
 
 #include <iterator>
 #include <memory>
 #include <string>
 
 #include "base/callback.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "content/browser/frame_host/frame_tree_node.h"
 #include "content/common/content_export.h"
 
 namespace content {
 
 struct FrameOwnerProperties;
 class Navigator;
 class RenderFrameHostDelegate;
-class RenderProcessHost;
 class RenderViewHostDelegate;
 class RenderViewHostImpl;
 class RenderFrameHostManager;
 class RenderWidgetHostDelegate;
 
 // Represents the frame tree for a page. With the exception of the main frame,
 // all FrameTreeNodes will be created/deleted in response to frame attach and
 // detach events in the DOM.
 //
 // The main frame's FrameTreeNode is special in that it is reused. This allows
@@ skipping 211 matching lines @@
 
   // Overall load progress.
   double load_progress_;
 
   DISALLOW_COPY_AND_ASSIGN(FrameTree);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_FRAME_TREE_H_