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

content/browser/renderer_host/input/touch_event_queue.h

Index: content/browser/renderer_host/input/touch_event_queue.h
diff --git a/content/browser/renderer_host/input/touch_event_queue.h b/content/browser/renderer_host/input/touch_event_queue.h
index 31a69fcb18eba261e87676d91e84ef21bace8421..5db421b62c83eaec30874796331c021b36a4bd86 100644
--- a/content/browser/renderer_host/input/touch_event_queue.h
+++ b/content/browser/renderer_host/input/touch_event_queue.h
@@ -242,6 +242,9 @@ class CONTENT_EXPORT TouchEventQueue {
   // 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);
 };