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

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

Index: third_party/WebKit/Source/core/inspector/ThreadDebugger.cpp
diff --git a/third_party/WebKit/Source/core/inspector/ThreadDebugger.cpp b/third_party/WebKit/Source/core/inspector/ThreadDebugger.cpp
index 5dce282cc4bfa53d316b71d1670785fe8e7325bc..ecdda6b0bec7a5524b6eb19f1029a6f01b3133d7 100644
--- a/third_party/WebKit/Source/core/inspector/ThreadDebugger.cpp
+++ b/third_party/WebKit/Source/core/inspector/ThreadDebugger.cpp
@@ -89,14 +89,22 @@ void ThreadDebugger::AsyncTaskCanceled(void* task) {
 }
 
 void ThreadDebugger::AllAsyncTasksCanceled() {
+  current_async_tasks_ = 0;
   v8_inspector_->allAsyncTasksCanceled();
 }
 
-void ThreadDebugger::AsyncTaskStarted(void* task) {
-  v8_inspector_->asyncTaskStarted(task);
+bool ThreadDebugger::AsyncTaskStarted(void* task, bool optional) {
+  if (!current_async_tasks_ || !optional) {
+    ++current_async_tasks_;
+    v8_inspector_->asyncTaskStarted(task);
+    return true;
+  }
+  return false;
 }
 
 void ThreadDebugger::AsyncTaskFinished(void* task) {
+  if (current_async_tasks_ > 0)
+    --current_async_tasks_;
   v8_inspector_->asyncTaskFinished(task);
 }