Rework standalone to use a synchronous loader that does not invoke Dart code

sdk/lib/vmservice/vmservice.dart

 // Copyright (c) 2015, 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 dart._vmservice;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:isolate';
 import 'dart:typed_data';
 
 part 'asset.dart';
 part 'client.dart';
 part 'constants.dart';
 part 'running_isolate.dart';
 part 'running_isolates.dart';
 part 'message.dart';
 part 'message_router.dart';
 
 final RawReceivePort isolateLifecyclePort = new RawReceivePort();
 final RawReceivePort scriptLoadPort = new RawReceivePort();
 
+// This is for use by the embedder. It is a map from the isolateId to
+// anything. When an isolate goes away, it will be removed from this map.
+final Map<int, dynamic> isolateEmbedderData = new Map<int, dynamic>();
+
 // These must be kept in sync with the declarations in vm/json_stream.h.
 const kInvalidParams = -32602;
 const kInternalError = -32603;
 const kStreamAlreadySubscribed = 103;
 const kStreamNotSubscribed = 104;
 
 var _errorMessages = {
   kInvalidParams: 'Invalid params',
   kInternalError: 'Internal error',
   kStreamAlreadySubscribed: 'Stream already subscribed',
@@ skipping 83 matching lines @@
   void _controlMessageHandler(int code,
                               int portId,
                               SendPort sp,
                               String name) {
     switch (code) {
       case Constants.ISOLATE_STARTUP_MESSAGE_ID:
         runningIsolates.isolateStartup(portId, sp, name);
       break;
       case Constants.ISOLATE_SHUTDOWN_MESSAGE_ID:
         runningIsolates.isolateShutdown(portId, sp);
+        isolateEmbedderData.remove(portId);
       break;
     }
   }
 
   Future _exit() async {
     // Stop the server.
     if (VMServiceEmbedderHooks.serverStop != null) {
       await VMServiceEmbedderHooks.serverStop();
     }
 
@@ skipping 196 matching lines @@
 external void onServerAddressChange(String address);
 
 /// Subscribe to a service stream.
 external bool _vmListenStream(String streamId);
 
 /// Cancel a subscription to a service stream.
 external void _vmCancelStream(String streamId);
 
 /// Get the bytes to the tar archive.
 external Uint8List _requestAssets();