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

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 3868 matching lines @@
                 rootDocumentListenerHistogram.count(toTouchTargetHistogramValue(eventTarget, domDispatchResult));
 
                 // Count the handled touch starts and first touch moves before and after the page is fully loaded respectively.
                 if (m_frame->document()->isLoadCompleted()) {
                     DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsAfterPageLoadHistogram, ("Event.Touch.TouchDispositionsAfterPageLoad", TouchEventDispatchResultTypeMax));
                     touchDispositionsAfterPageLoadHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : UnhandledTouches);
                 } else {
                     DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsBeforePageLoadHistogram, ("Event.Touch.TouchDispositionsBeforePageLoad", TouchEventDispatchResultTypeMax));
                     touchDispositionsBeforePageLoadHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : UnhandledTouches);
                 }
+
+                // Count the handled touch starts while there is an active fling animation.
+                if (event.type() == PlatformEvent::TouchStart && event.isFlingInProgress()) {
+                    DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsDuringFlingHistogram, ("Event.Touch.TouchDispositionsDuringFling", TouchEventDispatchResultTypeMax));
+                    touchDispositionsDuringFlingHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : UnhandledTouches);
+                }
             }
             eventResult = mergeEventResult(eventResult, toWebInputEventResult(domDispatchResult));
         }
     }
     return eventResult;
 }
 
 WebInputEventResult EventHandler::handleTouchEvent(const PlatformTouchEvent& event)
 {
     TRACE_EVENT0("blink", "EventHandler::handleTouchEvent");
@@ skipping 271 matching lines @@
 
 FrameHost* EventHandler::frameHost()
 {
     if (!m_frame->page())
         return nullptr;
 
     return &m_frame->page()->frameHost();
 }
 
 } // namespace blink