Add devtools trace event for event dispatching

Source/core/events/EventDispatcher.cpp

Index: Source/core/events/EventDispatcher.cpp
diff --git a/Source/core/events/EventDispatcher.cpp b/Source/core/events/EventDispatcher.cpp
index c4485eff66f80cd94cc96649f537921a2e70813a..45b5910d40cd4aa114d6f3186066a72415fc5199 100644
--- a/Source/core/events/EventDispatcher.cpp
+++ b/Source/core/events/EventDispatcher.cpp
@@ -33,6 +33,7 @@
 #include "core/events/WindowEventContext.h"
 #include "core/frame/FrameView.h"
 #include "core/inspector/InspectorInstrumentation.h"
+#include "platform/TraceEvent.h"
 #include "wtf/RefPtr.h"
 
 namespace WebCore {
@@ -112,6 +113,8 @@ bool EventDispatcher::dispatch()
     ASSERT(!NoEventDispatchAssertion::isEventDispatchForbidden());
     ASSERT(m_event->target());
     WindowEventContext windowEventContext(m_event.get(), m_node.get(), topNodeEventContext());
+    TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("devtools-timeline"), "EventDispatcher::dispatch", "type", TRACE_STR_COPY(m_event->type().ascii().data()));

[pfeldman, 2014/04/16 09:01:19]

"EventDispatcher::dispatchEvent"

[yurys, 2014/04/18 13:38:52]

Why? The method is called dispatch. I believe we should use either method name
as the trace event name or front-end name for that event, i.e. non-qualified
"EventDispatch".

+    // FIXME(361045): remove InspectorInstrumentation calls once DevTools Timeline migrated on tracing.

[pfeldman, 2014/04/16 09:01:19]

migrates to tracing.

[yurys, 2014/04/18 13:38:52]

Done.

     InspectorInstrumentationCookie cookie = InspectorInstrumentation::willDispatchEvent(&m_node->document(), *m_event, windowEventContext.window(), m_node.get(), m_event->eventPath());
 
     void* preDispatchEventHandlerResult;