Don't schedule an animation during compositing dirty-bit setting unless needed.

Source/core/page/PageAnimator.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 PageAnimator_h
 #define PageAnimator_h
 
 namespace WebCore {
 
 class Page;
 
 class PageAnimator {
 public:
     explicit PageAnimator(Page*);
 
     void scheduleVisualUpdate();
     void serviceScriptedAnimations(double monotonicAnimationStartTime);
 
     void setAnimationFramePending() { m_animationFramePending = true; }
     bool isServicingAnimations() const { return m_servicingAnimations; }
+    void updateLayoutAndStyleForPainting();
 
 private:
     Page* m_page;
     bool m_animationFramePending;
     bool m_servicingAnimations;
+    bool m_updatingLayoutAndStyleForPainting;
 };
 
 }
 
 #endif // PageAnimator_h