Bug 644637. Make sure mRequest lives long enough that we don't hand dead objects around. r=sdwilsh

uriloader/exthandler/nsExternalHelperAppService.h

@@ -444,10 +444,11 @@ protected:
   PRBool mKeepRequestAlive;
 
   /**
-   * The request that's being loaded. Not used after OnStopRequest, so a weak
+   * The request that's being loaded. Initialized in OnStartRequest.
-   * reference suffices. Initialized in OnStartRequest.
+   * Nulled out in OnStopRequest or once we know what we're doing
+   * with the data, whichever happens later.
    */
-  nsIRequest*  mRequest;
+  nsCOMPtr<nsIRequest> mRequest;
 };
 
 extern NS_HIDDEN_(nsExternalHelperAppService*) gExtProtSvc;