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

third_party/WebKit/public/web/WebInputEvent.h

Index: third_party/WebKit/public/web/WebInputEvent.h
diff --git a/third_party/WebKit/public/web/WebInputEvent.h b/third_party/WebKit/public/web/WebInputEvent.h
index 63837299dabd7772bda81521075d9656d6c3f11a..ca84282ff5e3d77867023c5a805dc81e0b8d12ba 100644
--- a/third_party/WebKit/public/web/WebInputEvent.h
+++ b/third_party/WebKit/public/web/WebInputEvent.h
@@ -633,6 +633,10 @@ public:
     // touch-point has moved (by whatever amount).
     bool movedBeyondSlopRegion;
 
+    // Whether there is an active fling animation when we dispatch the touch
+    // events.

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

Maybe something like:

// Whether there was an active fling animation when the event was dispatched.

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

Done.

+    bool dispatchedDuringFling;
+
     // A unique identifier for the touch event.
     uint32_t uniqueTouchEventId;
 
@@ -641,6 +645,7 @@ public:
         , touchesLength(0)
         , dispatchType(Blocking)
         , movedBeyondSlopRegion(false)
+        , dispatchedDuringFling(false)
         , uniqueTouchEventId(0)
     {
     }