Reduce service isolate startup time from ~80ms to ~30ms

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';
 
 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();
+
 class VMService extends MessageRouter {
   static VMService _instance;
   /// Collection of currently connected clients.
   final Set<Client> clients = new Set<Client>();
 
   // A map encoding which clients are interested in which kinds of events.
   final Map<int, Set<Client>> eventMap = new Map<int, Set<Client>>();
 
   /// Collection of currently running isolates.
   RunningIsolates runningIsolates = new RunningIsolates();
@@ skipping 68 matching lines @@
     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');
     }
   }
 
   VMService._internal()
-      : eventPort = new RawReceivePort() {
+      : eventPort = isolateLifecyclePort {
     eventPort.handler = messageHandler;
   }
 
   factory VMService() {
     if (VMService._instance == null) {
       VMService._instance = new VMService._internal();
+      _onStart();
     }
     return _instance;
   }
 
   void _clientCollection(Message message) {
     var members = [];
     var result = {};
     clients.forEach((client) {
       members.add(client.toJson());
     });
@@ skipping 11 matching lines @@
       return message.response;
     }
     if (message.path[0] == 'isolates') {
       return runningIsolates.route(message);
     }
     return message.sendToVM();
   }
 }
 
 RawReceivePort boot() {
-  // Boot the VMService.
   // Return the port we expect isolate startup and shutdown messages on.
-  return new VMService().eventPort;
+  return isolateLifecyclePort;
 }
 
 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";