Add UMA metric for tracking root level listeners for blocking touch.

third_party/WebKit/Source/core/events/EventTarget.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  *           (C) 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ skipping 155 matching lines @@
 
     virtual DispatchEventResult dispatchEventInternal(Event*);
 
     // Subclasses should likely not override these themselves; instead, they should subclass EventTargetWithInlineData.
     virtual EventTargetData* eventTargetData() = 0;
     virtual EventTargetData& ensureEventTargetData() = 0;
 
 private:
     LocalDOMWindow* executingWindow();
     void setDefaultAddEventListenerOptions(AddEventListenerOptions&);
-    void fireEventListeners(Event*, EventTargetData*, EventListenerVector&);
+    bool fireEventListeners(Event*, EventTargetData*, EventListenerVector&);
     void countLegacyEvents(const AtomicString& legacyTypeName, EventListenerVector*, EventListenerVector*);
 
     bool clearAttributeEventListener(const AtomicString& eventType);
 
     friend class EventListenerIterator;
 };
 
 // EventTargetData is a GCed object, so it should not be used as a part of
 // object. However, we intentionally use it as a part of object for performance,
 // assuming that no one extracts a pointer of
@@ skipping 68 matching lines @@
 {
     EventTargetData* d = eventTargetData();
     if (!d)
         return false;
     return d->eventListenerMap.containsCapturing(eventType);
 }
 
 } // namespace blink
 
 #endif // EventTarget_h