Record size of scroller that user scrolls

third_party/WebKit/Source/core/input/ScrollManager.h

Index: third_party/WebKit/Source/core/input/ScrollManager.h
diff --git a/third_party/WebKit/Source/core/input/ScrollManager.h b/third_party/WebKit/Source/core/input/ScrollManager.h
index 715282dc7264ee8f5f26fe50a967a9dc33677028..74c4672c4af592f52c12e1dfd950e60f7c77c846 100644
--- a/third_party/WebKit/Source/core/input/ScrollManager.h
+++ b/third_party/WebKit/Source/core/input/ScrollManager.h
@@ -111,8 +111,10 @@ class CORE_EXPORT ScrollManager
   void RecomputeScrollChain(const Node& start_node,
                             std::deque<int>& scroll_chain);
 
-  uint32_t ComputeNonCompositedMainThreadScrollingReasons();
-  void RecordNonCompositedMainThreadScrollingReasons(const WebGestureDevice);
+  void ComputeScrollRelatedMetrics(

[flackr, 2017/04/21 00:56:35]

Document that scroller_size is set only if there is a non root scroller?

[yigu, 2017/04/21 12:20:33]

Done.

+      uint32_t* non_composited_main_thread_scrolling_reasons,
+      int* scroller_size);
+  void RecordScrollRelatedMetrics(const WebGestureDevice);
 
   // NOTE: If adding a new field to this class please ensure that it is
   // cleared in |ScrollManager::clear()|.