Add devtools trace event for event dispatching

Source/core/frame/DOMWindow.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation 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.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 1586 matching lines @@
 {
     ASSERT(!NoEventDispatchAssertion::isEventDispatchForbidden());
 
     RefPtr<EventTarget> protect = this;
     RefPtrWillBeRawPtr<Event> event = prpEvent;
 
     event->setTarget(prpTarget ? prpTarget : this);
     event->setCurrentTarget(this);
     event->setEventPhase(Event::AT_TARGET);
 
+    TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("devtools-timeline"), "DOMWindow::dispatchEvent", "type", event->type().ascii());
+    // FIXME(361045): remove InspectorInstrumentation calls once DevTools Timeline migrates to tracing.
     InspectorInstrumentationCookie cookie = InspectorInstrumentation::willDispatchEventOnWindow(frame(), *event, this);
 
     bool result = fireEventListeners(event.get());
 
     InspectorInstrumentation::didDispatchEventOnWindow(cookie);
 
     return result;
 }
 
 void DOMWindow::removeAllEventListeners()
@@ skipping 269 matching lines @@
     visitor->trace(m_media);
     visitor->trace(m_sessionStorage);
     visitor->trace(m_localStorage);
     visitor->trace(m_applicationCache);
     visitor->trace(m_performance);
     visitor->trace(m_css);
     WillBeHeapSupplementable<DOMWindow>::trace(visitor);
 }
 
 } // namespace WebCore