optimizing layout performance when only transform3d matrix changed by

Source/core/dom/Document.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 1034 matching lines @@
 
     void registerVisibilityObserver(DocumentVisibilityObserver*);
     void unregisterVisibilityObserver(DocumentVisibilityObserver*);
 
     // FIXME: Remove this method once we have input routing in the browser
     // process. See http://crbug.com/339659.
     virtual void defaultEventHandler(Event*) OVERRIDE;
 
     void updateStyleInvalidationIfNeeded();
 
+    void setFastCompositing(bool enable) { m_fastCompositing = enable;}
 protected:
     Document(const DocumentInit&, DocumentClassFlags = DefaultDocumentClass);
 
     virtual void didUpdateSecurityOrigin() OVERRIDE FINAL;
 
     void clearXMLVersion() { m_xmlVersion = String(); }
 
     virtual void dispose() OVERRIDE;
 
     virtual PassRefPtr<Document> cloneDocumentWithoutChildren();
@@ skipping 281 matching lines @@
     Document* m_templateDocumentHost; // Manually managed weakref (backpointer from m_templateDocument).
 
     Timer<Document> m_didAssociateFormControlsTimer;
     HashSet<RefPtr<Element> > m_associatedFormControls;
 
     HashSet<SVGUseElement*> m_useElementsNeedingUpdate;
 
     bool m_hasViewportUnits;
 
     HashSet<DocumentVisibilityObserver*> m_visibilityObservers;
+
+    bool m_fastCompositing;
 };
 
 inline void Document::notifyRemovePendingSheetIfNeeded()
 {
     if (m_needsNotifyRemoveAllPendingStylesheet)
         didRemoveAllPendingStylesheet();
 }
 
 inline bool Document::shouldOverrideLegacyDescription(ViewportDescription::Type origin)
 {
@@ skipping 34 matching lines @@
 inline bool Node::isDocumentNode() const
 {
     return this == document();
 }
 
 Node* eventTargetNodeForDocument(Document*);
 
 } // namespace WebCore
 
 #endif // Document_h