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 9a6f9cf21449f09ecf6aa557fe529e1456dcf83c..cf84b29b5caa42c2fd9c7028149b1bfa14526315 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 was an active fling animation when the event was
+    // dispatched.
+    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)
     {
     }