UMA metrics for use count of wheel and touch scrolls.

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

 // 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.
 
 #include "core/input/ScrollManager.h"
 
 #include <memory>
 #include "core/dom/DOMNodeIds.h"
 #include "core/events/GestureEvent.h"
 #include "core/frame/BrowserControls.h"
@@ skipping 217 matching lines @@
   scrollStateData->position_x = position.x();
   scrollStateData->position_y = position.y();
   scrollStateData->is_beginning = true;
   scrollStateData->from_user_input = true;
   scrollStateData->is_direct_manipulation =
       gestureEvent.sourceDevice == WebGestureDeviceTouchscreen;
   scrollStateData->delta_consumed_for_scroll_sequence =
       m_deltaConsumedForScrollSequence;
   ScrollState* scrollState = ScrollState::create(std::move(scrollStateData));
   customizedScroll(*m_scrollGestureHandlingNode.get(), *scrollState);
+
+  if (gestureEvent.sourceDevice == WebGestureDeviceTouchscreen)
+    UseCounter::count(m_frame->document(), UseCounter::ScrollByTouch);
+  else
+    UseCounter::count(m_frame->document(), UseCounter::ScrollByWheel);
+
   return WebInputEventResult::HandledSystem;
 }
 
 WebInputEventResult ScrollManager::handleGestureScrollUpdate(
     const WebGestureEvent& gestureEvent) {
   DCHECK_EQ(gestureEvent.type(), WebInputEvent::GestureScrollUpdate);
 
   Node* node = m_scrollGestureHandlingNode.get();
   if (!node || !node->layoutObject())
     return WebInputEventResult::NotHandled;
@@ skipping 305 matching lines @@
     if (scrollbar->gestureEvent(targetedEvent.event(), &shouldUpdateCapture)) {
       if (shouldUpdateCapture)
         m_scrollbarHandlingScrollGesture = scrollbar;
       return true;
     }
   }
   return false;
 }
 
 }  // namespace blink