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

third_party/WebKit/Source/platform/PlatformTouchEvent.h

Index: third_party/WebKit/Source/platform/PlatformTouchEvent.h
diff --git a/third_party/WebKit/Source/platform/PlatformTouchEvent.h b/third_party/WebKit/Source/platform/PlatformTouchEvent.h
index 97afb62f8860ec3892588efb50d7c46644915a43..107b872d3f7217a452479d3d8d5bd93422e83b6d 100644
--- a/third_party/WebKit/Source/platform/PlatformTouchEvent.h
+++ b/third_party/WebKit/Source/platform/PlatformTouchEvent.h
@@ -32,6 +32,7 @@ public:
         : PlatformEvent(PlatformEvent::TouchStart)
         , m_dispatchType(PlatformEvent::Blocking)
         , m_causesScrollingIfUncanceled(false)
+        , m_isFlingInProgress(false)
     {
     }
 
@@ -40,11 +41,13 @@ public:
     DispatchType dispatchType() const { return m_dispatchType; }
     bool cancelable() const { return m_dispatchType == PlatformEvent::Blocking; }
     bool causesScrollingIfUncanceled() const { return m_causesScrollingIfUncanceled; }
+    bool isFlingInProgress() const { return m_isFlingInProgress; }
 
 protected:
     Vector<PlatformTouchPoint> m_touchPoints;
     DispatchType m_dispatchType;
     bool m_causesScrollingIfUncanceled;
+    bool m_isFlingInProgress;
 };
 
 } // namespace blink