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

content/browser/renderer_host/input/touch_event_queue.h

 // Copyright 2013 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_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_
 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 224 matching lines @@
   // uncancelable touchmoves which are still waiting for their acks back from
   // render. We do not put them back to the front the touch_event_queue any
   // more.
   std::deque<uint32_t> ack_pending_async_touchmove_ids_;
 
   double last_sent_touch_timestamp_sec_;
 
   // Event is saved to compare pointer positions for new touchmove events.
   std::unique_ptr<blink::WebTouchEvent> last_sent_touchevent_;
 
+  // True if a GestureFlingStart happens and false after a GestureFlingCancel.

[tdresser, 2016/04/28 19:02:41]

Have you confirmed that a GFC gets sent at the correct time on both the main and
compositor threads?

[lanwei, 2016/04/28 20:25:18]

Yes, I tested for both the main and compositor threads, Fling gestures are sent
here.

+  bool fling_in_progress_;
+
   DISALLOW_COPY_AND_ASSIGN(TouchEventQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_