Bug 1183394 - Remove the assertion message when shutdown. r=jwwang

dom/html/HTMLMediaElement.cpp

@@ -1211,6 +1211,7 @@ nsresult HTMLMediaElement::LoadResource()
       // TODO: Handle failure: run "If the media data cannot be fetched at
       // all, due to network errors, causing the user agent to give up
       // trying to fetch the resource" section of resource fetch algorithm.
+      decoder->Shutdown();
       return NS_ERROR_FAILURE;
     }
     nsRefPtr<MediaResource> resource =