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

third_party/WebKit/Source/core/inspector/ThreadDebugger.h

Index: third_party/WebKit/Source/core/inspector/ThreadDebugger.h
diff --git a/third_party/WebKit/Source/core/inspector/ThreadDebugger.h b/third_party/WebKit/Source/core/inspector/ThreadDebugger.h
index 7b1cf23a985a0b9dc240544697736bbac9765cc4..dd01349d14e368a78d9331215eb395f369b82353 100644
--- a/third_party/WebKit/Source/core/inspector/ThreadDebugger.h
+++ b/third_party/WebKit/Source/core/inspector/ThreadDebugger.h
@@ -43,7 +43,7 @@ class CORE_EXPORT ThreadDebugger : public v8_inspector::V8InspectorClient,
   void AsyncTaskScheduled(const String& task_name, void* task, bool recurring);
   void AsyncTaskCanceled(void* task);
   void AllAsyncTasksCanceled();
-  void AsyncTaskStarted(void* task);
+  bool AsyncTaskStarted(void* task, bool optional);
   void AsyncTaskFinished(void* task);
   unsigned PromiseRejected(v8::Local<v8::Context>,
                            const String& error_message,
@@ -110,6 +110,8 @@ class CORE_EXPORT ThreadDebugger : public v8_inspector::V8InspectorClient,
   Vector<v8_inspector::V8InspectorClient::TimerCallback> timer_callbacks_;
   Vector<void*> timer_data_;
   std::unique_ptr<UserGestureIndicator> user_gesture_indicator_;
+
+  int current_async_tasks_ = 0;
 };
 
 }  // namespace blink