Clean up forward declarations in core/rendering and core/painting

Source/core/paint/ReplicaPainter.h

 // Copyright 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 ReplicaPainter_h
 #define ReplicaPainter_h
 
 namespace blink {
 
 struct PaintInfo;
 class LayoutPoint;
-class RenderBox;
 class RenderReplica;
 
 class ReplicaPainter {
 public:
     ReplicaPainter(RenderReplica& renderReplica) : m_renderReplica(renderReplica) { }
 
     void paint(PaintInfo&, const LayoutPoint& paintOffset);
 
 private:
     RenderReplica& m_renderReplica;
 };
 
 } // namespace blink
 
 #endif // ReplicaPainter_h