Add UseCounters for Event.cancelBubble behavior.

third_party/WebKit/Source/core/events/Event.cpp

 /*
  * Copyright (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2001 Tobias Anton (anton@stud.fbi.fh-darmstadt.de)
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2005, 2006, 2008 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 340 matching lines @@
             Performance* performance = DOMWindowPerformance::performance(*scriptState->domWindow());
             timeStamp = performance->monotonicTimeToDOMHighResTimeStamp(m_platformTimeStamp);
         }
     } else {
         timeStamp = m_createTime;
     }
 
     return timeStamp;
 }
 
+void Event::setCancelBubble(ExecutionContext* context, bool cancel)
+{
+    if (!m_cancelBubble && cancel)
+        UseCounter::count(context, UseCounter::EventCancelBubbleWasChangedToTrue);
+    else if (m_cancelBubble && !cancel)
+        UseCounter::count(context, UseCounter::EventCancelBubbleWasChangedToFalse);
+    m_cancelBubble = cancel;
+}
+
 DEFINE_TRACE(Event)
 {
     visitor->trace(m_currentTarget);
     visitor->trace(m_target);
     visitor->trace(m_underlyingEvent);
     visitor->trace(m_eventPath);
 }
 
 } // namespace blink