Add implementation of Isolate.resolvePackageUri for dart2js.

tests/isolate/browser/package_resolve_browser_hook_test.dart

+// Copyright (c) 2015, 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.
+
+import 'dart:isolate';
+import 'package:unittest/unittest.dart';
+
+final PACKAGE_URI = "package:foo/bar.txt";

[Lasse Reichstein Nielsen, 2016/11/14 20:42:34]

Nitpick: Style guide says to use camelCase for constants. :)

[Siggi Cherem (dart-lang), 2016/11/14 23:07:15]

haha - good point, I just copied it from a different test. Honestly we don't
need a constant here :)

+
+main() async {

[Lasse Reichstein Nielsen, 2016/11/14 20:42:34]

Are you sure an async main works with the test runner? I've had problems with
that in some cases (but I never figured out exactly which cases)

[Siggi Cherem (dart-lang), 2016/11/14 23:07:15]

Good point, should be fixed now.

+  var uri = await Isolate.resolvePackageUri(Uri.parse(PACKAGE_URI));
+  expect(uri, Uri.base.resolve('path_set_from_hook/foo/bar.txt'));

[Harry Terkelsen, 2016/11/14 22:27:23]

can we also test if the hook is set to a path with slashes in it?

[Siggi Cherem (dart-lang), 2016/11/14 23:07:15]

Done.

+}