Measure Event.returnValue usage in more detail

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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #include "config.h"
 #include "core/events/Event.h"
 
 #include "core/dom/StaticNodeList.h"
 #include "core/events/EventTarget.h"
+#include "core/frame/UseCounter.h"
 #include "wtf/CurrentTime.h"
 
 namespace WebCore {
 
 EventInit::EventInit()
     : bubbles(false)
     , cancelable(false)
 {
 }
 
@@ skipping 56 matching lines @@
 
     m_propagationStopped = false;
     m_immediatePropagationStopped = false;
     m_defaultPrevented = false;
 
     m_type = eventTypeArg;
     m_canBubble = canBubbleArg;
     m_cancelable = cancelableArg;
 }
 
+bool Event::legacyReturnValue(ExecutionContext* executionContext) const
+{
+    bool returnValue = !defaultPrevented();
+    if (returnValue)
+        UseCounter::count(executionContext, UseCounter::EventGetReturnValueTrue);
+    else
+        UseCounter::count(executionContext, UseCounter::EventGetReturnValueFalse);
+    return returnValue;
+}
+
+void Event::setLegacyReturnValue(ExecutionContext* executionContext, bool returnValue)
+{
+    if (returnValue)
+        UseCounter::count(executionContext, UseCounter::EventSetReturnValueTrue);
+    else
+        UseCounter::count(executionContext, UseCounter::EventSetReturnValueFalse);
+    setDefaultPrevented(!returnValue);
+}
+
 const AtomicString& Event::interfaceName() const
 {
     return EventNames::Event;
 }
 
 bool Event::hasInterface(const AtomicString& name) const
 {
     return interfaceName() == name;
 }
 
@@ skipping 99 matching lines @@
     return StaticNodeList::createEmpty();
 }
 
 void Event::trace(Visitor* visitor)
 {
     visitor->trace(m_underlyingEvent);
     visitor->trace(m_eventPath);
 }
 
 } // namespace WebCore