Bug#31228: Patch from : roc+moz@cs.cmu.edu (Robert O'Callahan). Thanks Robert! r:pnunn.

gfx/src/nsImageNetContextAsync.cpp

@@ -363,7 +363,7 @@ ImageConsumer::OnDataAvailable(nsIChannel* channel, nsISupports* aContext, nsIIn
   }
 
   nsresult err = 0;
-  PRUint32 nb;
+  PRUint32 nb = 0;
   char* uriStr = NULL;
   nsCOMPtr<nsIURI> uri;