optimizing layout performance when only transform3d matrix changed by

Source/core/dom/Document.cpp

 /*
  * 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, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 461 matching lines @@
     , m_elementDataCacheClearTimer(this, &Document::elementDataCacheClearTimerFired)
 #ifndef NDEBUG
     , m_didDispatchViewportPropertiesChanged(false)
 #endif
     , m_animationClock(AnimationClock::create())
     , m_timeline(DocumentTimeline::create(this))
     , m_transitionTimeline(TransitionTimeline::create(this))
     , m_templateDocumentHost(0)
     , m_didAssociateFormControlsTimer(this, &Document::didAssociateFormControlsTimerFired)
     , m_hasViewportUnits(false)
+    , m_fastCompositing(false)
 {
     setClient(this);
     ScriptWrappable::init(this);
 
     if (m_frame) {
         ASSERT(m_frame->page());
         provideContextFeaturesToDocumentFrom(*this, *m_frame->page());
 
         m_fetcher = m_frame->loader().documentLoader()->fetcher();
     }
@@ skipping 1298 matching lines @@
         if (StyleResolverStats* stats = ensureStyleResolver().stats())
             stats->reset();
 
         if (Element* documentElement = this->documentElement()) {
             inheritHtmlAndBodyElementStyles(change);
             if (documentElement->shouldCallRecalcStyle(change))
                 documentElement->recalcStyle(change);
         }
 
         ensureStyleResolver().printStats();
-
-        view()->updateCompositingLayersAfterStyleChange();
+        view()->updateCompositingLayersAfterStyleChange(m_fastCompositing);
+        m_fastCompositing = true;
 
         clearChildNeedsStyleRecalc();
 
         if (m_styleEngine->hasResolver()) {
             // Pseudo element removal and similar may only work with these flags still set. Reset them after the style recalc.
             StyleResolver& resolver = m_styleEngine->ensureResolver();
             m_styleEngine->resetCSSFeatureFlags(resolver.ensureUpdatedRuleFeatureSet());
             resolver.clearStyleSharingList();
         }
 
@@ skipping 3631 matching lines @@
 }
 
 void Document::invalidateNodeListCaches(const QualifiedName* attrName)
 {
     HashSet<LiveNodeListBase*>::iterator end = m_listsInvalidatedAtDocument.end();
     for (HashSet<LiveNodeListBase*>::iterator it = m_listsInvalidatedAtDocument.begin(); it != end; ++it)
         (*it)->invalidateCache(attrName);
 }
 
 } // namespace WebCore