Let deferred load work from worker isolates.

tools/testing/dart/http_server.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 http_server;
 
 import 'dart:async';
 import 'dart:io';
 import 'test_suite.dart';  // For TestUtils.
 // TODO(efortuna): Rewrite to not use the args library and simply take an
@@ skipping 77 matching lines @@
  */
 class TestingServers {
   static final _CACHE_EXPIRATION_IN_SECONDS = 30;
   static final _HARMLESS_REQUEST_PATH_ENDINGS = [
     "/apple-touch-icon.png",
     "/apple-touch-icon-precomposed.png",
     "/favicon.ico",
     "/foo",
     "/bar",
     "/NonExistingFile",
+    "/NonExistingFile.js",
     "/hahaURL",
   ];
 
   List _serverList = [];
   Path _buildDirectory = null;
   final bool useContentSecurityPolicy;
   final String runtime;
 
   TestingServers(Path buildDirectory,
                  this.useContentSecurityPolicy,
@@ skipping 278 matching lines @@
 class _Entry {
   final String name;
   final String displayName;
 
   _Entry(this.name, this.displayName);
 
   int compareTo(_Entry other) {
     return name.compareTo(other.name);
   }
 }