Load CMA backend from shared library

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>
 
 #include "chromecast_export.h"
 
 namespace chromecast {
 namespace media {
 
+class MediaPipelineBackend;
+struct MediaPipelineDeviceParams;
 class VideoPlane;
 
 // Provides access to platform-specific media systems and hardware resources.
 // In cast_shell, all usage is from the browser process.  An implementation is
 // assumed to be in an uninitialized state initially.  When uninitialized, no
 // API calls will be made except for Initialize, which brings the implementation
 // into an initialized state.  A call to Finalize returns the implementation to
 // its uninitialized state.  The implementation must support multiple
 // transitions between these states, to support resource grant/revoke events and
 // also to allow multiple unit tests to bring up the media systems in isolation
 // from other tests.
 class CHROMECAST_EXPORT CastMediaShlib {
  public:
   // Initializes platform-specific media systems.  Only called when in an
   // uninitialized state.
   static void Initialize(const std::vector<std::string>& argv);
 
   // 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();

[alokp, 2015/08/10 20:30:25]

Please document ownership for the returned VideoPlane object. I am assuming that
the backend owns the video plane?

+
+  // 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
+  static MediaPipelineBackend* CreateMediaPipelineBackend(

[alokp, 2015/08/10 20:30:25]

Who owns the returned MediaPipelineBackend? I am assuming the caller, in which
case, shouldn't it return a scoped_ptr? If the motivation is to not depend on
chrome base, we should at least document the ownership or use std::unique_ptr.

+      const MediaPipelineDeviceParams& params);
 };
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_PUBLIC_CAST_MEDIA_SHLIB_H_