Support percent encoded data URIs in the standalone embedder.

runtime/tests/vm/dart/data_uri_spawn_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";
+
+Uri toDartDataUri(String source) {
+  return Uri.parse("data:application/dart;charset=utf-8,"
+                   "${Uri.encodeComponent(source)}");
+}
+
+main() {
+  test('Simple response', () {
+    String source = """
+import "dart:isolate";
+main(List args, SendPort replyPort) {
+  print('Child running');
+  replyPort.send(42);
+}
+""";
+
+    RawReceivePort receivePort;
+    receivePort = new RawReceivePort(expectAsync((int message) {
+      expect(message, equals(42));
+      receivePort.close();
+    }));
+    Isolate.spawnUri(toDartDataUri(source), [], receivePort.sendPort);
+  });
+}