First cut at _spawnUri rpc in the vm service.

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';
@@ skipping 277 matching lines @@
       return encodeRpcError(message, kStreamNotSubscribed);
     }
     client.streams.remove(streamId);
     if (!_isAnyClientSubscribed(streamId)) {
       _vmCancelStream(streamId);
     }
 
     return encodeSuccess(message);
   }
 
+  Future<String> _spawnUri(Message message) async {
+    var token = message.params['token'];
+    if (token == null) {
+      return encodeMissingParamError(message, 'token');

[Cutch, 2016/07/07 16:17:45]

here you allow for any object as the token but in _spawnUriNotify and related C
code you expect it to be a String. Maybe validate that here and reject
non-string tokens?

[turnidge, 2016/07/11 21:24:59]

Done.

+    }
+    var uri = message.params['uri'];
+    if (uri == null) {
+      return encodeMissingParamError(message, 'uri');
+    }
+    if (uri is! String) {
+      return encodeInvalidParamError(message, 'uri');
+    }
+    var args = message.params['args'];
+    if (args != null &&
+        args is! List<String>) {
+      return encodeInvalidParamError(message, 'args');
+    }
+    var msg = message.params['message'];
+
+    Isolate.spawnUri(Uri.parse(uri), args, msg).then((isolate) {
+      _spawnUriNotify(isolate.controlPort, token);
+    }).catchError((e) {
+      _spawnUriNotify(e.toString(), token);
+    });
+
+    return encodeSuccess(message);
+  }
+
   // TODO(johnmccutchan): Turn this into a command line tool that uses the
   // service library.
   Future<String> _getCrashDump(Message message) async {
     var client = message.client;
     final perIsolateRequests = [
         // ?isolateId=<isolate id> will be appended to each of these requests.
         // Isolate information.
         Uri.parse('getIsolate'),
         // State of heap.
         Uri.parse('_getAllocationProfile'),
@@ skipping 52 matching lines @@
     // TODO(turnidge): Update to json rpc.  BEFORE SUBMIT.
     if (message.method == '_getCrashDump') {
       return _getCrashDump(message);
     }
     if (message.method == 'streamListen') {
       return _streamListen(message);
     }
     if (message.method == 'streamCancel') {
       return _streamCancel(message);
     }
+    if (message.method == '_spawnUri') {
+      return _spawnUri(message);
+    }
     if (_devfs.shouldHandleMessage(message)) {
       return _devfs.handleMessage(message);
     }
     if (message.params['isolateId'] != null) {
       return runningIsolates.route(message);
     }
     return message.sendToVM();
   }
 }
 
@@ skipping 17 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();
+
+/// Notify the vm service that an isolate has been spawned via rpc.
+external void _spawnUriNotify(obj, String token);