*** NOT FOR LANDING *** Paint investigations for bug 667370

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

Index: third_party/WebKit/Source/core/paint/PrePaintTreeWalk.cpp
diff --git a/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.cpp b/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.cpp
index b2eb801927b03127b62f45e9f9560cb2f3cd1617..3fc177880ca6c9e4d486004430d386b1890a6881 100644
--- a/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.cpp
+++ b/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.cpp
@@ -37,6 +37,8 @@ struct PrePaintTreeWalkContext {
 };
 
 void PrePaintTreeWalk::walk(FrameView& rootFrame) {
+  TRACE_EVENT0("blink", "PrePaintTreeWalk::walk");
+
   DCHECK(rootFrame.frame().document()->lifecycle().state() ==
          DocumentLifecycle::InPrePaint);
 
@@ -205,7 +207,7 @@ void PrePaintTreeWalk::invalidatePaintLayerOptimizationsIfNeeded(
     paintLayer.setPreviousPaintPhaseDescendantBlockBackgroundsEmpty(false);
     // All subsequences which are contained below this paintLayer must also
     // be checked.
-    context.forceSubtreeUpdate = true;
+//    context.forceSubtreeUpdate = true;
   }
 
   paintLayer.setPreviousPaintingClipRects(*clipRects);