Rename blahHandler to onBlah throughout dart:io.

tests/standalone/src/TestingServer.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2012, 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.
 
 class TestingServer extends Isolate {
 
   static final HOST = "127.0.0.1";
   static final INIT = 0;
   static final SHUTDOWN = -1;
 
   abstract void connectionHandler();
 
   void main() {
     void errorHandlerServer() {
       Expect.fail("Server socket error");
     }
 
     this.port.receive((message, SendPort replyTo) {
       if (message == INIT) {
         _server = new ServerSocket(HOST, 0, 10);
         Expect.equals(true, _server !== null);
-        _server.connectionHandler = connectionHandler;
-        _server.errorHandler = errorHandlerServer;
+        _server.onConnection = connectionHandler;
+        _server.onError = errorHandlerServer;
         replyTo.send(_server.port, null);
       } else if (message == SHUTDOWN) {
         _server.close();
         this.port.close();
       }
     });
   }
 
   ServerSocket _server;
 }