back out http channel loadFlags to fix regression 172376

modules/plugin/base/src/nsPluginHostImpl.cpp

@@ -5826,7 +5826,7 @@ nsresult nsPluginHostImpl::NewEmbededPluginStream(nsIURI* aURL,
     nsCOMPtr<nsIChannel> channel;
 
     rv = NS_NewChannel(getter_AddRefs(channel), aURL, nsnull, loadGroup, nsnull,
-       nsIChannel::LOAD_DOCUMENT_URI /* to handle onload for this url */);
+       /* prevents throbber from becoming active */ nsIRequest::LOAD_BACKGROUND);
     if (NS_SUCCEEDED(rv)) {
       // if this is http channel, set referrer, some servers are configured
       // to reject requests without referrer set, see bug 157796