Reland of Messaging: Avoid calling non-thread-safe functions in MessagePort::messageAvailable()

third_party/WebKit/Source/core/dom/MessagePort.h

Index: third_party/WebKit/Source/core/dom/MessagePort.h
diff --git a/third_party/WebKit/Source/core/dom/MessagePort.h b/third_party/WebKit/Source/core/dom/MessagePort.h
index dc6835a60c2c32c7a341fbf63082efefbe6f706c..afeb451a4d6397846deb305cc67c0f45fcd158b8 100644
--- a/third_party/WebKit/Source/core/dom/MessagePort.h
+++ b/third_party/WebKit/Source/core/dom/MessagePort.h
@@ -34,6 +34,7 @@
 #include "core/dom/ContextLifecycleObserver.h"
 #include "core/events/EventListener.h"
 #include "core/events/EventTarget.h"
+#include "platform/WebTaskRunner.h"
 #include "platform/wtf/PassRefPtr.h"
 #include "platform/wtf/RefPtr.h"
 #include "platform/wtf/Vector.h"
@@ -140,9 +141,11 @@
 
   std::unique_ptr<WebMessagePortChannel> entangled_channel_;
 
-  int pending_dispatch_task_;
-  bool started_;
-  bool closed_;
+  int pending_dispatch_task_ = 0;
+  bool started_ = false;
+  bool closed_ = false;
+
+  RefPtr<WebTaskRunner> task_runner_;
 };
 
 }  // namespace blink