Make mojo renderer capable of supporting multiple streams/tracks

media/mojo/interfaces/renderer.mojom

Index: media/mojo/interfaces/renderer.mojom
diff --git a/media/mojo/interfaces/renderer.mojom b/media/mojo/interfaces/renderer.mojom
index 38ca4401b4b1d429464448095d14ed3ff85e5cc2..e5bb78cdd3d773cd08b8a610c14ea8c1083da2bf 100644
--- a/media/mojo/interfaces/renderer.mojom
+++ b/media/mojo/interfaces/renderer.mojom
@@ -12,11 +12,10 @@ 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);