Specify packageRoot parameter to Isolate.spawnUri.

sdk/lib/_internal/compiler/js_lib/isolate_patch.dart

 // Copyright (c) 2012, 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.
 
 // Patch file for the dart:isolate library.
 
 import 'dart:_js_helper' show patch;
 import 'dart:_isolate_helper' show CapabilityImpl,
                                    CloseToken,
                                    IsolateNatives,
@@ skipping 11 matching lines @@
           .then((msg) => new Isolate(msg[1],
                                      pauseCapability: msg[2],
                                      terminateCapability: msg[3]));
     } catch (e, st) {
       return new Future<Isolate>.error(e, st);
     }
   }
 
   @patch
   static Future<Isolate> spawnUri(
-      Uri uri, List<String> args, var message, { bool paused: false }) {
+      Uri uri, List<String> args, var message, { bool paused: false,
+                                                 Uri packageRoot }) {
+    if (packageRoot != null) throw new UnimplementedError("packageRoot");
     try {
       if (args is List<String>) {
         for (int i = 0; i < args.length; i++) {
           if (args[i] is! String) {
             throw new ArgumentError("Args must be a list of Strings $args");
           }
         }
       } else if (args != null) {
         throw new ArgumentError("Args must be a list of Strings $args");
       }
@@ skipping 99 matching lines @@
   factory RawReceivePort([void handler(event)]) {
     return new RawReceivePortImpl(handler);
   }
 }
 
 @patch
 class Capability {
   @patch
   factory Capability() = CapabilityImpl;
 }