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

third_party/WebKit/Source/core/input/TouchEventManager.cpp

Index: third_party/WebKit/Source/core/input/TouchEventManager.cpp
diff --git a/third_party/WebKit/Source/core/input/TouchEventManager.cpp b/third_party/WebKit/Source/core/input/TouchEventManager.cpp
index 5fbb1139f481d6dcf3bea6dfe89f759b3deb01d4..49ad089693043d8f70d70b33232c262b3f16dd55 100644
--- a/third_party/WebKit/Source/core/input/TouchEventManager.cpp
+++ b/third_party/WebKit/Source/core/input/TouchEventManager.cpp
@@ -251,6 +251,17 @@ WebInputEventResult TouchEventManager::dispatchTouchEvents(
                     DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsBeforePageLoadHistogram, ("Event.Touch.TouchDispositionsBeforePageLoad", TouchEventDispatchResultTypeMax));
                     touchDispositionsBeforePageLoadHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : UnhandledTouches);
                 }
+
+                // Count the handled touch starts while there is and isn't an active fling animation.

[tdresser, 2016/05/13 13:42:21]

Report the touch disposition, split by whether there is an active fling
animation.

[lanwei, 2016/05/13 18:15:48]

Done.

+                if (event.type() == PlatformEvent::TouchStart) {
+                    if (event.dispatchedDuringFling()) {
+                        DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsDuringFlingHistogram, ("Event.Touch.TouchDispositionsDuringFling", TouchEventDispatchResultTypeMax));
+                        touchDispositionsDuringFlingHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : UnhandledTouches);
+                    } else {
+                        DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsNoFlingHistogram, ("Event.Touch.TouchDispositionsNoFling", TouchEventDispatchResultTypeMax));
+                        touchDispositionsNoFlingHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : UnhandledTouches);
+                    }
+                }
             }
             eventResult = EventHandler::mergeEventResult(eventResult,
                 EventHandler::toWebInputEventResult(domDispatchResult));