Make mojo renderer capable of supporting multiple streams/tracks

media/mojo/interfaces/renderer.mojom

 // Copyright 2014 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.mojom;
 
 import "media/mojo/interfaces/demuxer_stream.mojom";
 import "media/mojo/interfaces/media_types.mojom";
 import "mojo/common/time.mojom";
 import "mojo/common/unguessable_token.mojom";
 import "ui/gfx/geometry/mojo/geometry.mojom";
 import "url/mojo/url.mojom";
 
 interface Renderer {
-  // Initializes the Renderer with one or both of an audio and video stream,
+  // Initializes the Renderer with one or more audio / video streams,
   // executing the callback with whether the initialization succeeded.
   Initialize(associated RendererClient client,
-             DemuxerStream? audio,
-             DemuxerStream? video,
+             array<DemuxerStream> streams,

[xhwang, 2017/01/31 00:15:21]

Should this be optional if we actually use URL based rendering? Or |stream| will
be empty in this case?

[servolk, 2017/01/31 01:10:40]

Done (made the streams parameter optional, also updated the comment to explain
that it's either streams or media_url).

              url.mojom.Url? media_url,
              url.mojom.Url? first_party_for_cookies) => (bool success);
 
   // Discards any buffered data, executing callback when completed.
   // NOTE: If an error occurs, RendererClient::OnError() can be called
   // before the callback is executed.
   Flush() => ();
 
   // Starts rendering from |time|.
   StartPlayingFrom(mojo.common.mojom.TimeDelta time);
@@ skipping 53 matching lines @@
   OnStatisticsUpdate(PipelineStatistics stats);
 
   // Called when the remote renderering service is waiting on the decryption
   // key.
   OnWaitingForDecryptionKey();
 
   // Executed the first time the metadata is updated, and whenever the duration
   // changes.
   OnDurationChange(mojo.common.mojom.TimeDelta duration);
 };