Motown: Add examples/media_test, a command line media player app.

mojo/services/media/control/interfaces/media_source.mojom

 // 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.
 
 [DartPackage="mojo_services"]
 module mojo.media;
 
 import "mojo/services/media/common/interfaces/media_clock.mojom";
 import "mojo/services/media/common/interfaces/media_common.mojom";
 import "mojo/services/media/common/interfaces/media_metadata.mojom";
 import "mojo/services/media/common/interfaces/media_state.mojom";
 import "mojo/services/media/common/interfaces/media_transport.mojom";
 import "mojo/services/media/common/interfaces/media_types.mojom";
 
 // Produces media streams delivered from a specified origin.
 interface MediaSource {
+  // Special value for GetStatus version_last_seen parameter to get the current
+  // status immediately.
+  const uint64 kInitialStatus = 0;
+
   // Gets the streams produced by this source.
   GetStreams() => (array<MediaSourceStreamDescriptor> streams);
 
   // Gets the clock disposition from the source.
   GetClockDisposition() => (ClockDisposition clock_disposition);
 
   // Gets a master clock if the source can be master, null otherwise.
   GetMasterClock(Clock& master_clock);
 
   // Sets a master clock.
   SetMasterClock(Clock? master_clock);
 
   // Gets the producer for the specified stream.
   GetProducer(uint32 stream_index, MediaProducer& producer);
 
   // Gets the pull mode producer for the specified stream.
   GetPullModeProducer(uint32 stream_index, MediaPullModeProducer& producer);
 
-  // Gets the status. To get the status immediately, call GetStatus(0). To
-  // get updates thereafter, pass the version sent in the previous callback.
+  // Gets the status. To get the status immediately, call
+  // GetStatus(kInitialStatus). To get updates thereafter, pass the version
+  // sent in the previous callback.
   GetStatus(uint64 version_last_seen) =>
       (uint64 version, MediaSourceStatus status);
 
   // Prepares the source.
   Prepare() => ();
 
   // Primes the source and downstream components.
   Prime() => ();
 
   // Flushes the source and downstream components.
@@ skipping 16 matching lines @@
 };
 
 // Describes the media source.
 struct MediaSourceStatus {
   // Current state of the source.
   MediaState state;
 
   // Describes the media.
   MediaMetadata? metadata;
 };