Add second argument to Future error handlers.

tests/lib/async/catch_errors.dart

 library catch_errors;
 
 import 'dart:async';
 
 Stream catchErrors(void body()) {
   StreamController controller;
 
-  bool onError(e) {
+  bool onError(e, st) {
     controller.add(e);
     return true;
   }
 
   void onListen() {
     runZoned(body, onError: onError);
   }
 
   controller = new StreamController(onListen: onListen);
   return controller.stream;
 }