Add UMA metric for tracking listeners for blocking touch while fling is happening

content/renderer/input/main_thread_event_queue.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 CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_H_
 #define CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_H_
 
 #include <deque>
 #include "content/common/content_export.h"
 #include "content/common/input/event_with_latency_info.h"
@@ skipping 82 matching lines @@
 class CONTENT_EXPORT MainThreadEventQueue {
  public:
   MainThreadEventQueue(int routing_id, MainThreadEventQueueClient* client);
   ~MainThreadEventQueue();
 
   // Called once the compositor has handled |event| and indicated that it is
   // a non-blocking event to be queued to the main thread.
   bool HandleEvent(const blink::WebInputEvent* event,
                    const ui::LatencyInfo& latency,
                    InputEventDispatchType dispatch_type,
-                   InputEventAckState ack_result);
+                   InputEventAckState ack_result,
+                   bool is_flinging = false);

[tdresser, 2016/05/09 19:48:45]

Can we plumb the information about whether a fling is active separately from the
handle event call?

We should be able to tell the main thread event queue when fling starts and
stops, instead of adding this bit.

[lanwei, 2016/05/12 11:50:36]

Done.

 
   // Call once the main thread has handled an outstanding |type| event
   // in flight.
   void EventHandled(blink::WebInputEvent::Type type);
 
  private:
   friend class MainThreadEventQueueTest;
   int routing_id_;
   MainThreadEventQueueClient* client_;
   WebInputEventQueue<PendingMouseWheelEvent> wheel_events_;
   WebInputEventQueue<PendingTouchEvent> touch_events_;
 
   DISALLOW_COPY_AND_ASSIGN(MainThreadEventQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_H_