[Chromecast] Upgrade to new CMA backend API

chromecast/public/cast_media_shlib.h

 // 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.
 
 #ifndef CHROMECAST_PUBLIC_CAST_MEDIA_SHLIB_H_
 #define CHROMECAST_PUBLIC_CAST_MEDIA_SHLIB_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 24 matching lines @@
   // Tears down platform-specific media systems and returns to the uninitialized
   // state.  The implementation must release all media-related hardware
   // resources.
   static void Finalize();
 
   // Gets the VideoPlane instance for managing the hardware video plane.
   // While an implementation is in an initialized state, this function may be
   // called at any time.  The VideoPlane object must be destroyed in Finalize.
   static VideoPlane* GetVideoPlane();
 
-  // Creates a factory object for a media pipeline backend.  Called in the
-  // browser process, any number of times (once per media pipeline).  Each call
-  // must instantiate a new factory object
+  // Creates a media pipeline backend.  Called in the browser process for each
+  // media pipeline and raw audio stream.

[slan, 2015/10/06 19:34:00]

Even though each MediaPipelineBackend must be able to return 3+1 A/V decoders,
this interface returns a single global instance, and ownership is retained. Can
we add these details to the comment?

[kmackay, 2015/10/06 21:44:55]

Updated the comments. This function is called once to create a new backend
instance for each new media playback stream.

[slan, 2015/10/06 22:15:05]

Thanks, much clearer.

   static MediaPipelineBackend* CreateMediaPipelineBackend(
       const MediaPipelineDeviceParams& params);
 };
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_PUBLIC_CAST_MEDIA_SHLIB_H_