Reduce forward declarations in core/rendering

Source/core/rendering/RenderFlowThread.h

 /*
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 23 matching lines @@
 #include "core/rendering/RenderBlockFlow.h"
 #include "wtf/HashCountedSet.h"
 #include "wtf/ListHashSet.h"
 #include "wtf/PassRefPtr.h"
 
 namespace WebCore {
 
 struct LayerFragment;
 typedef Vector<LayerFragment, 1> LayerFragments;
 class RenderFlowThread;
-class RenderStyle;
 class RenderRegion;
 
 typedef ListHashSet<RenderRegion*> RenderRegionList;
 
 // RenderFlowThread is used to collect all the render objects that participate in a
 // flow thread. It will also help in doing the layout. However, it will not render
 // directly to screen. Instead, RenderRegion objects will redirect their paint
 // and nodeAtPoint methods to this object. Each RenderRegion will actually be a viewPort
 // of the RenderFlowThread.
 
@@ skipping 160 matching lines @@
 };
 
 template <> struct ValueToString<RenderRegion*> {
     static String string(const RenderRegion* value) { return String::format("%p", value); }
 };
 #endif
 
 } // namespace WebCore
 
 #endif // RenderFlowThread_h