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

sdk/lib/isolate/isolate.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.
 
 /**
  * Concurrent programming using _isolates_:
  * independent workers that are similar to threads
  * but don't share memory,
  * communicating only via messages.
  */
@@ skipping 194 matching lines @@
    * If the parameter is omitted, the new isolate will inherit the
    * value from the current isolate.
    *
    * It may not always be possible to honor the `checked` parameter.
    * If the isolate code was pre-compiled, it may not be possible to change
    * the checked mode setting dynamically.
    * In that case, the `checked` parameter is ignored.
    *
    * WARNING: The [checked] parameter is not implemented on all platforms yet.
    *
-   * If the [packageRoot] parameter is provided, it is used to find the location
-   * of packages imports in the spawned isolate.
+   * If either the [packageRoot] or the [packages] parameter is provided,
+   * it is used to find the location of package sources in the spawned isolate.
+   *
    * The `packageRoot` URI must be a "file" or "http"/"https" URI that specifies
    * a directory. If it doesn't end in a slash, one will be added before
    * using the URI, and any query or fragment parts are ignored.
-   * Package imports (like "package:foo/bar.dart") in the new isolate are
+   * Package imports (like `"package:foo/bar.dart"`) in the new isolate are
    * resolved against this location, as by
    * `packageRoot.resolve("foo/bar.dart")`.
-   * This includes the main entry [uri] if it happens to be a package-URL.
-   * If [packageRoot] is omitted, it defaults to the same URI that
-   * the current isolate is using.
    *
-   * WARNING: The [packageRoot] parameter is not implemented on all
-   * platforms yet.
+   * The `packages` map maps package names to URIs with the same requirements
+   * as `packageRoot`. Package imports (like `"package:foo/bar/baz.dart"`) in
+   * the new isolate are resolved against the URI for that package (if any),
+   * as by `packages["foo"].resolve("bar/baz.dart")
+   *
+   * This resolution also applies to the main entry [uri]
+   * if that happens to be a package-URI.
+   *
+   * If both [packageRoot] and [packages] are omitted, the new isolate uses
+   * the same package resolution as the current isolate.
+   * It's not allowed to provide both a `packageRoot` and a `package` parameter.
+   *
+   * WARNING: The [packageRoot] and [packages] parameters are not implemented
+   * on all platforms yet.
    *
    * Returns a future that will complete with an [Isolate] instance if the
    * spawning succeeded. It will complete with an error otherwise.
    */
   external static Future<Isolate> spawnUri(
       Uri uri,
       List<String> args,
       var message,
       {bool paused: false,
        bool checked,
        Uri packageRoot,
+       Map<String, Uri> packages,
        bool errorsAreFatal,
        SendPort onExit,
        SendPort onError});
 
   /**
    * Requests the isolate to pause.
    *
    * The isolate should stop handling events by pausing its event queue.
    * The request will eventually make the isolate stop doing anything.
    * It will be handled before any other messages that are later sent to the
@@ skipping 386 matching lines @@
  * as the original error, but has no other features of the original error.
  */
 class RemoteError implements Error {
   final String _description;
   final StackTrace stackTrace;
   RemoteError(String description, String stackDescription)
       : _description = description,
         stackTrace = new StackTrace.fromString(stackDescription);
   String toString() => _description;
 }