Optimize the pre-paint tree walk and ClipRects

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

Index: third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
index 8165be07c17c0a1bc1d635920683fca0955c750e..e32ca9f3705cfe02bfffd34581ac81b75da623f1 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
@@ -228,9 +228,8 @@ static bool shouldRepaintSubsequence(
         paintLayer.clipper(PaintLayer::DoNotUseGeometryMapper)
             .paintingClipRects(paintingInfo.rootLayer, respectOverflowClip,
                                subpixelAccumulation);
-    ClipRects* previousClipRects = paintLayer.previousPaintingClipRects();
-    if (&clipRects != previousClipRects &&
-        (!previousClipRects || clipRects != *previousClipRects)) {
+    if (!paintLayer.hasPreviousPaintingClipRects() ||
+        clipRects != paintLayer.previousPaintingClipRects()) {
       needsRepaint = true;
       shouldClearEmptyPaintPhaseFlags = true;
     }