Cleanup: Remove unused include headers and forward declarations

Source/core/rendering/compositing/CompositingReasonFinder.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 CompositingReasonFinder_h
 #define CompositingReasonFinder_h
 
 #include "core/rendering/RenderLayer.h"
 #include "core/rendering/compositing/CompositingTriggers.h"
 #include "platform/graphics/CompositingReasons.h"
 
 namespace WebCore {
 
-class RenderLayer;
 class RenderObject;
 class RenderView;
 
 class CompositingReasonFinder {
     WTF_MAKE_NONCOPYABLE(CompositingReasonFinder);
 public:
     explicit CompositingReasonFinder(RenderView&);
 
     CompositingReasons styleDeterminedReasons(RenderObject*) const;
     CompositingReasons directReasons(const RenderLayer*) const;
@@ skipping 15 matching lines @@
     bool requiresCompositingForPositionSticky(RenderObject*, const RenderLayer*) const;
     bool requiresCompositingForPositionFixed(RenderObject*, const RenderLayer*, RenderLayer::ViewportConstrainedNotCompositedReason*) const;
 
     RenderView& m_renderView;
     CompositingTriggerFlags m_compositingTriggers;
 };
 
 } // namespace WebCore
 
 #endif // CompositingReasonFinder_h