Revert r43217, r43215, r43208, r43207, and r43202.

runtime/vm/service/vmservice.dart

 // Copyright (c) 2013, 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.
 
 library vmservice;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:isolate';
 import 'dart:typed_data';
@@ skipping 88 matching lines @@
     assert(message is List);
     if (message is List && message.length == 4) {
       _controlMessageHandler(message[0], message[1], message[2], message[3]);
     } else if (message is List && message.length == 2) {
       _eventMessageHandler(message[0], message[1]);
     } else {
       Logger.root.severe('Unexpected message: $message');
     }
   }
 
-  void _notSupported(_) {
-    throw new UnimplementedError('Service script loading not supported.');
-  }
-
   VMService._internal()
       : eventPort = isolateLifecyclePort {
-    scriptLoadPort.handler = _notSupported;
     eventPort.handler = messageHandler;
   }
 
   factory VMService() {
     if (VMService._instance == null) {
       VMService._instance = new VMService._internal();
       _onStart();
     }
     return _instance;
   }
@@ skipping 31 matching lines @@
 
 void _registerIsolate(int port_id, SendPort sp, String name) {
   var service = new VMService();
   service.runningIsolates.isolateStartup(port_id, sp, name);
 }
 
 void _setEventMask(int mask)
     native "VMService_SetEventMask";
 
 void _onStart() native "VMService_OnStart";