Optimize the pre-paint tree walk and ClipRects

third_party/WebKit/Source/core/paint/PaintLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 77 matching lines @@
 
 namespace blink {
 
 namespace {
 
 static CompositingQueryMode gCompositingQueryMode =
     CompositingQueriesAreOnlyAllowedInCertainDocumentLifecyclePhases;
 
 struct SameSizeAsPaintLayer : DisplayItemClient {
   int bitFields;
-  void* pointers[11];
+  void* pointers[10];
   LayoutUnit layoutUnits[4];
   IntSize size;
   Persistent<PaintLayerScrollableArea> scrollableArea;
   struct {
     IntSize size;
     void* pointer;
     LayoutRect rect;
   } previousPaintStatus;
+  ClipRects previousClipRects;
 };
 
 static_assert(sizeof(PaintLayer) == sizeof(SameSizeAsPaintLayer),
               "PaintLayer should stay small");
 
 bool isReferenceClipPath(const ClipPathOperation* clipOperation) {
   return clipOperation && clipOperation->type() == ClipPathOperation::REFERENCE;
 }
 
 }  // namespace
@@ skipping 32 matching lines @@
       m_needsPaintPhaseDescendantOutlines(false),
       m_previousPaintPhaseDescendantOutlinesWasEmpty(false),
       m_needsPaintPhaseFloat(false),
       m_previousPaintPhaseFloatWasEmpty(false),
       m_needsPaintPhaseDescendantBlockBackgrounds(false),
       m_previousPaintPhaseDescendantBlockBackgroundsWasEmpty(false),
       m_hasDescendantWithClipPath(false),
       m_hasNonIsolatedDescendantWithBlendMode(false),
       m_hasAncestorWithClipPath(false),
       m_selfPaintingStatusChanged(false),
+      m_hasPreviousPaintingClipRects(false),
       m_layoutObject(layoutObject),
       m_parent(0),
       m_previous(0),
       m_next(0),
       m_first(0),
       m_last(0),
       m_staticInlinePosition(0),
       m_staticBlockPosition(0),
       m_ancestorOverflowLayer(nullptr) {
   updateStackingNode();
@@ skipping 3081 matching lines @@
 }
 
 void showLayerTree(const blink::LayoutObject* layoutObject) {
   if (!layoutObject) {
     LOG(INFO) << "Cannot showLayerTree. Root is (nil)";
     return;
   }
   showLayerTree(layoutObject->enclosingLayer());
 }
 #endif