Add a sky media service to make it possible to play a sound.

sky/services/media/media.mojom

Index: sky/services/media/media.mojom
diff --git a/sky/services/media/media.mojom b/sky/services/media/media.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..39e7b26e02ecb79f7cd483f534c9fff399d0dbb5
--- /dev/null
+++ b/sky/services/media/media.mojom
@@ -0,0 +1,17 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+module media;
+
+interface MediaPlayer {
+  // ignored argument due to https://github.com/domokit/mojo/issues/282
+  prepare(handle<data_pipe_consumer> data_source) => (bool ignored);
+  start();
+  pause();
+  seekTo(uint32 msec);
+};
+
+interface MediaService {
+  createPlayer(MediaPlayer& player);
+};