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

Source/core/rendering/ClipRectsCache.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 ClipRectsCache_h
 #define ClipRectsCache_h
 
 #include "core/rendering/ClipRects.h"
 
 #if ENABLE(ASSERT)
 #include "core/rendering/RenderBox.h" // For OverlayScrollbarSizeRelevancy.
 #endif
 
 namespace blink {
 
+class RenderLayer;
+
 enum ClipRectsCacheSlot {
     // Relative to the ancestor treated as the root (e.g. transformed layer). Used for hit testing.
     RootRelativeClipRects,
 
     // Relative to the RenderView's layer. Used for compositing overlap testing.
     AbsoluteClipRects,
 
     // Relative to painting ancestor. Used for painting.
     PaintingClipRects,
     PaintingClipRectsIgnoringOverflowClip,
@@ skipping 33 matching lines @@
         m_entries[slot] = Entry();
     }
 
 private:
     Entry m_entries[NumberOfClipRectsCacheSlots];
 };
 
 } // namespace blink
 
 #endif // ClipRectsCache_h