Add `packages` parameter to `Isolate.spawnUri`.

sdk/lib/_internal/js_runtime/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 44 matching lines @@
             return isolate;
           });
     } 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, bool checked, Uri packageRoot, bool errorsAreFatal,
-       SendPort onExit, SendPort onError}) {
+      {bool paused: false,
+       bool checked,
+       Uri packageRoot,
+       Map<String, Uri> packages,
+       bool errorsAreFatal,
+       SendPort onExit,
+       SendPort onError}) {
     if (packageRoot != null) throw new UnimplementedError("packageRoot");
+    if (packages != null) throw new UnimplementedError("packages");
     bool forcePause = (errorsAreFatal != null) ||
                       (onExit != null) ||
                       (onError != null);
     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");
       }
+      // TODO: Handle [packageRoot]/[packages] somehow, possibly by throwing.
       // TODO: Consider passing the errorsAreFatal/onExit/onError values
       //       as arguments to the internal spawnUri instead of setting
       //       them after the isolate has been created.
       return IsolateNatives.spawnUri(uri, args, message, paused || forcePause)
           .then((msg) {
             var isolate = new Isolate(msg[1],
                                       pauseCapability: msg[2],
                                       terminateCapability: msg[3]);
             if (forcePause) {
               if (errorsAreFatal != null) {
@@ skipping 112 matching lines @@
   factory RawReceivePort([void handler(event)]) {
     return new RawReceivePortImpl(handler);
   }
 }
 
 @patch
 class Capability {
   @patch
   factory Capability() = CapabilityImpl;
 }