Bug 1164834: MessageEvents coming from postMessage should not be cancelable. r=Ms2ger

dom/workers/WorkerPrivate.cpp

@@ -1147,7 +1147,7 @@ public:
     nsresult rv =
       event->InitMessageEvent(NS_LITERAL_STRING("message"),
                               false /* non-bubbling */,
-                              true /* cancelable */,
+                              false /* non-cancelable */,
                               messageData,
                               EmptyString(),
                               EmptyString(),

testing/web-platform/meta/workers/interfaces/DedicatedWorkerGlobalScope/postMessage/message-event.html.ini

@@ -1,6 +0,0 @@
-[message-event.html]
-  type: testharness
-  [Properties of the 'message' event]
-    expected: FAIL
-    bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1164834
-