Record size of scroller that user scrolls

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ScrollManager_h
 #define ScrollManager_h
 
 #include <deque>
 #include "core/CoreExport.h"
 #include "core/page/EventWithHitTestResults.h"
@@ skipping 93 matching lines @@
 
   Page* GetPage() const;
 
   bool IsViewportScrollingElement(const Element&) const;
 
   bool HandleScrollGestureOnResizer(Node*, const WebGestureEvent&);
 
   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()|.
 
   const Member<LocalFrame> frame_;
 
   // Only used with the ScrollCustomization runtime enabled feature.
   std::deque<int> current_scroll_chain_;
 
   Member<Node> scroll_gesture_handling_node_;
@@ skipping 17 matching lines @@
 
   Member<PaintLayerScrollableArea> resize_scrollable_area_;
 
   LayoutSize
       offset_from_resize_corner_;  // In the coords of m_resizeScrollableArea.
 };
 
 }  // namespace blink
 
 #endif  // ScrollManager_h