Add more specific metrics for main thread scrolling reasons

third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h

Index: third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
diff --git a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
index 69db4d7633a5f893650a663b27cf3e18eb469c1d..7efe0dea33bff073fc41bdc46f20f5f5fc0582c8 100644
--- a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
+++ b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
@@ -99,6 +99,10 @@ class CORE_EXPORT ScrollingCoordinator final
   bool shouldUpdateScrollLayerPositionOnMainThread() const {
     return mainThreadScrollingReasons() != 0;
   }
+  void removeStyleRelatedMainThreadScrollingReasonsForLayer(ScrollableArea*);

[bokan, 2016/12/19 21:25:14]

"ForLayer" is redundant, just leave it off.

[yigu, 2016/12/20 01:41:20]

Done.

+  void adjustStyleRelatedMainThreadScrollingReasons(const uint32_t reason,
+                                                    bool increase);
+  MainThreadScrollingReasons getStyleRelatedMainThreadScrollingReasons() const;
 
   std::unique_ptr<WebScrollbarLayer> createSolidColorScrollbarLayer(
       ScrollbarOrientation,
@@ -189,6 +193,11 @@ class CORE_EXPORT ScrollingCoordinator final
   bool m_wasFrameScrollable;
 
   MainThreadScrollingReasons m_lastMainThreadScrollingReasons;
+  // For recording main thread scrolling reasons
+  // due to layout object properties. e.g. opacity, transform.
+  // The size of the vector depends on the number of
+  // main thread scrolling reasons.
+  Vector<int> m_mainThreadScrollingReasonsCounter;
 };
 
 }  // namespace blink