InitEvent should not do anything if dispatch flag is set.

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

Index: third_party/WebKit/Source/core/events/MessageEvent.cpp
diff --git a/third_party/WebKit/Source/core/events/MessageEvent.cpp b/third_party/WebKit/Source/core/events/MessageEvent.cpp
index 6c676b67e811384d5ef130692e630d01c925b8a3..33bb457d70078d2e1fe5f6e59c174346cf934a0f 100644
--- a/third_party/WebKit/Source/core/events/MessageEvent.cpp
+++ b/third_party/WebKit/Source/core/events/MessageEvent.cpp
@@ -140,7 +140,7 @@ MessageEvent* MessageEvent::create(const AtomicString& type, const MessageEventI
 
 void MessageEvent::initMessageEvent(const AtomicString& type, bool canBubble, bool cancelable, ScriptValue data, const String& origin, const String& lastEventId, DOMWindow* source, MessagePortArray* ports)
 {
-    if (dispatched())
+    if (isBeingDispatched())
         return;
 
     initEvent(type, canBubble, cancelable);
@@ -156,7 +156,7 @@ void MessageEvent::initMessageEvent(const AtomicString& type, bool canBubble, bo
 
 void MessageEvent::initMessageEvent(const AtomicString& type, bool canBubble, bool cancelable, PassRefPtr<SerializedScriptValue> data, const String& origin, const String& lastEventId, DOMWindow* source, MessagePortArray* ports)
 {
-    if (dispatched())
+    if (isBeingDispatched())
         return;
 
     initEvent(type, canBubble, cancelable);