Optimize the pre-paint tree walk and ClipRects

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

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. 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 883 matching lines @@
   // shouldCreateSubsequence() in PaintLayerPainter.cpp for the cases we use
   // subsequence when painting a PaintLayer.
 
   IntSize previousScrollOffsetAccumulationForPainting() const {
     return m_previousScrollOffsetAccumulationForPainting;
   }
   void setPreviousScrollOffsetAccumulationForPainting(const IntSize& s) {
     m_previousScrollOffsetAccumulationForPainting = s;
   }
 
-  ClipRects* previousPaintingClipRects() const {
-    return m_previousPaintingClipRects.get();
+  bool hasPreviousPaintingClipRects() const {
+    return m_hasPreviousPaintingClipRects;
   }
-  void setPreviousPaintingClipRects(ClipRects& clipRects) {
-    m_previousPaintingClipRects = &clipRects;
+
+  const ClipRects& previousPaintingClipRects() const {
+    return m_previousPaintingClipRects;
+  }
+
+  void setPreviousPaintingClipRects(const ClipRects& clipRects) {
+    m_previousPaintingClipRects = clipRects;
+    m_hasPreviousPaintingClipRects = true;
   }
 
   LayoutRect previousPaintDirtyRect() const { return m_previousPaintDirtyRect; }
   void setPreviousPaintDirtyRect(const LayoutRect& rect) {
     m_previousPaintDirtyRect = rect;
   }
 
   PaintResult previousPaintResult() const {
     return static_cast<PaintResult>(m_previousPaintResult);
   }
@@ skipping 274 matching lines @@
   unsigned m_previousPaintPhaseDescendantBlockBackgroundsWasEmpty : 1;
 
   // These bitfields are part of ancestor/descendant dependent compositing
   // inputs.
   unsigned m_hasDescendantWithClipPath : 1;
   unsigned m_hasNonIsolatedDescendantWithBlendMode : 1;
   unsigned m_hasAncestorWithClipPath : 1;
 
   unsigned m_selfPaintingStatusChanged : 1;
 
+  unsigned m_hasPreviousPaintingClipRects : 1;
+
   LayoutBoxModelObject& m_layoutObject;
 
   PaintLayer* m_parent;
   PaintLayer* m_previous;
   PaintLayer* m_next;
   PaintLayer* m_first;
   PaintLayer* m_last;
 
   // Our (x,y) coordinates are in our containing layer's coordinate space.
   LayoutPoint m_location;
@@ skipping 15 matching lines @@
   std::unique_ptr<AncestorDependentCompositingInputs>
       m_ancestorDependentCompositingInputs;
 
   Persistent<PaintLayerScrollableArea> m_scrollableArea;
 
   mutable std::unique_ptr<ClipRectsCache> m_clipRectsCache;
 
   std::unique_ptr<PaintLayerStackingNode> m_stackingNode;
 
   IntSize m_previousScrollOffsetAccumulationForPainting;
-  RefPtr<ClipRects> m_previousPaintingClipRects;
+  ClipRects m_previousPaintingClipRects;
   LayoutRect m_previousPaintDirtyRect;
 
   std::unique_ptr<PaintLayerRareData> m_rareData;
 
   FRIEND_TEST_ALL_PREFIXES(PaintLayerTest,
                            DescendantDependentFlagsStopsAtThrottledFrames);
   FRIEND_TEST_ALL_PREFIXES(PaintLayerTest,
                            PaintLayerTransformUpdatedOnStyleTransformAnimation);
 };
 
 }  // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 CORE_EXPORT void showLayerTree(const blink::PaintLayer*);
 CORE_EXPORT void showLayerTree(const blink::LayoutObject*);
 #endif
 
 #endif  // Layer_h