[DevTools] added creation stack for event listeners without scheduled stack

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

Index: third_party/WebKit/Source/core/events/EventTarget.cpp
diff --git a/third_party/WebKit/Source/core/events/EventTarget.cpp b/third_party/WebKit/Source/core/events/EventTarget.cpp
index c3d395b70091abac31014faee6c00a895e1481b3..37e8e85c81da21249cab7aaf84880176793f3d7a 100644
--- a/third_party/WebKit/Source/core/events/EventTarget.cpp
+++ b/third_party/WebKit/Source/core/events/EventTarget.cpp
@@ -290,6 +290,8 @@ bool EventTarget::AddEventListenerInternal(
   if (!listener)
     return false;
 
+  probe::AsyncTaskScheduled(GetExecutionContext(), event_type, listener);
+
   V8DOMActivityLogger* activity_logger =
       V8DOMActivityLogger::CurrentActivityLoggerIfIsolatedWorld();
   if (activity_logger) {
@@ -709,6 +711,7 @@ bool EventTarget::FireEventListeners(Event* event,
     bool passive_forced = registered_listener.PassiveForcedForDocumentTarget();
 
     probe::UserCallback probe(context, nullptr, event->type(), false, this);
+    probe::AsyncTask async_task(context, listener, "Event Listener called");
 
     // To match Mozilla, the AT_TARGET phase fires both capturing and bubbling
     // event listeners, even though that violates some versions of the DOM spec.