Load Observatory assets lazily

runtime/bin/vmservice/vmservice_io.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_io;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
@@ skipping 10 matching lines @@
 bool _autoStart;
 
 bool _isWindows = false;
 
 var _signalWatch;
 var _signalSubscription;
 
 // HTTP server.
 Server server;
 Future<Server> serverFuture;
-HashMap<String, Asset> assets;
+HashMap<String, Asset> _assets;
+HashMap<String, Asset> get assets {
+  if (_assets == null) {
+    try {
+      _assets = Asset.request();
+    } catch (e) {
+      print('Could not load Observatory assets: $e');
+    }
+  }
+  return _assets;
+}
 
 _onShutdown() {
   if (server != null) {
     server.close(true).catchError((e, st) {
       print("Error in vm-service shutdown: $e\n$st\n");
     });
   }
   if (_signalSubscription != null) {
     _signalSubscription.cancel();
     _signalSubscription = null;
   }
 }
 
 _bootServer() {
-  try {
-    assets = Asset.request();
-  } catch (e) {
-    print('Could not load Observatory assets: $e');
-  }
   // Lazily create service.
   var service = new VMService();
   service.onShutdown = _onShutdown;
   // Lazily create server.
   server = new Server(service, _ip, _port);
 }
 
 _clearFuture(_) {
   serverFuture = null;
 }
@@ skipping 40 matching lines @@
   // else {
   //   var service = new VMService();
   //   service.onShutdown = _onShutdown;
   // }
   scriptLoadPort.handler = _processLoadRequest;
   // Register signal handler after a small delay to avoid stalling main
   // isolate startup.
   new Timer(_shortDelay, _registerSignalHandler);
   return scriptLoadPort;
 }