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 b5775ab80f437659a1792d800a4e512b198bac16..404cd537e37dbedf89e5e27d1753beef6894daac 100644
--- a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
+++ b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
@@ -98,6 +98,8 @@ class CORE_EXPORT ScrollingCoordinator final
   bool shouldUpdateScrollLayerPositionOnMainThread() const {
     return mainThreadScrollingReasons() != 0;
   }
+  void adjustMainThreadReasonsFromStyle(uint32_t reason, bool increase);
+  MainThreadScrollingReasons getMainThreadScrollingReasonsFromStyle() const;
 
   std::unique_ptr<WebScrollbarLayer> createSolidColorScrollbarLayer(
       ScrollbarOrientation,
@@ -184,6 +186,11 @@ 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