Fix broken test.

tests/isolate/src/MintMakerPromiseTest.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 interface Mint factory MintImpl {
 
   Mint();
 
   Purse createPurse(int balance);
 
@@ skipping 117 matching lines @@
 // THE REST OF THIS FILE COULD BE AUTOGENERATED
 // ---------------------------------------------------------------------------
 
 interface Mint$Proxy {
 
   Purse$Proxy createPurse(int balance);  // Promise<int> balance.
 
 }
 
 
-class Mint$ProxyImpl extends Proxy implements Mint$Proxy {
+class Mint$ProxyImpl extends ProxyImpl implements Mint$Proxy {
 
   Mint$ProxyImpl(Proxy isolate) : super.forReply(isolate.call([null])) {}
 
   Purse$Proxy createPurse(int balance) {
     return new Purse$ProxyImpl(this.call([balance]));
   }
 
 }
 
 
@@ skipping 29 matching lines @@
 
 interface Purse$Proxy {
 
   Promise<int> queryBalance();
   Purse$Proxy sproutPurse();
   Promise<int> deposit(int amount, Purse$Proxy source);  // Promise<int> amount.
 
 }
 
 
-class Purse$ProxyImpl extends Proxy implements Purse$Proxy {
+class Purse$ProxyImpl extends ProxyImpl implements Purse$Proxy {
 
   Purse$ProxyImpl(Promise<SendPort> port) : super.forReply(port) { }
 
   Promise<int> queryBalance() {
     return this.call(["balance"]);
   }
 
   Promise<int> deposit(int amount, Purse$Proxy source) {
     return this.call(["deposit", amount, source]);
   }
@@ skipping 33 matching lines @@
       reply("Exception: Command not understood");
     }
     //print("command $command done");
   }
 
 }
 
 main() {
   MintMakerPromiseTest.testMain();
 }