optimizing layout performance when only transform3d matrix changed by

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 588 matching lines @@
             hMode = ScrollbarAlwaysOff;
         } else if (Element* viewportElement = document->viewportDefiningElement()) {
             if (RenderObject* viewportRenderer = viewportElement->renderer()) {
                 if (viewportRenderer->style())
                     applyOverflowToViewportAndSetRenderer(viewportRenderer, hMode, vMode);
             }
         }
     }
 }
 
-void FrameView::updateCompositingLayersAfterStyleChange()
+void FrameView::updateCompositingLayersAfterStyleChange(bool fast)
 {
     TRACE_EVENT0("webkit", "FrameView::updateCompositingLayersAfterStyleChange");
     RenderView* renderView = this->renderView();
     if (!renderView)
         return;
 
     // If we expect to update compositing after an incipient layout, don't do so here.
     if (m_doingPreLayoutStyleUpdate || layoutPending() || renderView->needsLayout())
         return;
 
     // FIXME: Remove incremental compositing updates after fixing the chicken/egg issues
     // https://code.google.com/p/chromium/issues/detail?id=343756
     DisableCompositingQueryAsserts disabler;
 
     // This call will make sure the cached hasAcceleratedCompositing is updated from the pref
     renderView->compositor()->cacheAcceleratedCompositingFlags();
 
     // Sometimes we will change a property (for example, z-index) that will not
     // cause a layout, but will require us to update compositing state. We only
     // need to do this if a layout is not already scheduled.
     if (!needsLayout())
         renderView->compositor()->updateCompositingRequirementsState();
-
-    renderView->compositor()->setNeedsCompositingUpdate(CompositingUpdateAfterStyleChange);
+    CompositingUpdateType update = fast? CompositingMinUpdateAfterStyleChange: CompositingUpdateAfterStyleChange;
+    renderView->compositor()->setNeedsCompositingUpdate(update);
 }
 
 void FrameView::updateCompositingLayersAfterLayout()
 {
     TRACE_EVENT0("webkit", "FrameView::updateCompositingLayersAfterLayout");
     RenderView* renderView = this->renderView();
     if (!renderView)
         return;
 
     // FIXME: Remove incremental compositing updates after fixing the chicken/egg issues
@@ skipping 2570 matching lines @@
 void FrameView::willRemoveScrollbar(Scrollbar* scrollbar, ScrollbarOrientation orientation)
 {
     ScrollableArea::willRemoveScrollbar(scrollbar, orientation);
     if (AXObjectCache* cache = axObjectCache()) {
         cache->remove(scrollbar);
         cache->handleScrollbarUpdate(this);
     }
 }
 
 } // namespace WebCore