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

content/renderer/input/main_thread_event_queue.h

Index: content/renderer/input/main_thread_event_queue.h
diff --git a/content/renderer/input/main_thread_event_queue.h b/content/renderer/input/main_thread_event_queue.h
index 0eb2d147f8970e9aac457503e80a691300fb5fa5..6a99636a9a0d2f0851d7404b89778eb676a733a8 100644
--- a/content/renderer/input/main_thread_event_queue.h
+++ b/content/renderer/input/main_thread_event_queue.h
@@ -106,12 +106,15 @@ class CONTENT_EXPORT MainThreadEventQueue {
   // in flight.
   void EventHandled(blink::WebInputEvent::Type type);
 
+  void set_is_flinging(bool is_flinging) { is_flinging_ = is_flinging; }
+
  private:
   friend class MainThreadEventQueueTest;
   int routing_id_;
   MainThreadEventQueueClient* client_;
   WebInputEventQueue<PendingMouseWheelEvent> wheel_events_;
   WebInputEventQueue<PendingTouchEvent> touch_events_;
+  bool is_flinging_;
 
   DISALLOW_COPY_AND_ASSIGN(MainThreadEventQueue);
 };