Bug 1453525 - Remove OOM check of infallible method. r=mccr8

--HG--
extra : rebase_source : 2cbe66638e3a77417414bd8ca3ae9e7bf37d5b2c

dom/base/EventSource.cpp

@@ -1454,11 +1454,7 @@ EventSourceImpl::DispatchCurrentMessageEvent()
     message->mLastEventID.Assign(mLastEventID);
   }
 
-  size_t sizeBefore = mMessagesToDispatch.GetSize();
   mMessagesToDispatch.Push(message.release());
-  NS_ENSURE_TRUE(mMessagesToDispatch.GetSize() == sizeBefore + 1,
-                 NS_ERROR_OUT_OF_MEMORY);
-
 
   if (!mGoingToDispatchAllMessages) {
     nsCOMPtr<nsIRunnable> event =