Reduce forward declarations in core/rendering

Source/core/rendering/RenderFrameSet.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Simon Hausmann <hausmann@kde.org>
  * Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 12 matching lines @@
 #ifndef RenderFrameSet_h
 #define RenderFrameSet_h
 
 #include "core/rendering/RenderBox.h"
 
 namespace WebCore {
 
 class HTMLDimension;
 class HTMLFrameSetElement;
 class MouseEvent;
-class RenderFrame;
 
 enum FrameEdge { LeftFrameEdge, RightFrameEdge, TopFrameEdge, BottomFrameEdge };
 
 struct FrameEdgeInfo {
     FrameEdgeInfo(bool preventResize = false, bool allowBorder = true)
         : m_preventResize(4)
         , m_allowBorder(4)
     {
         m_preventResize.fill(preventResize);
         m_allowBorder.fill(allowBorder);
@@ skipping 87 matching lines @@
 
     bool m_isResizing;
     bool m_isChildResizing;
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderFrameSet, isFrameSet());
 
 } // namespace WebCore
 
 #endif // RenderFrameSet_h