Add documentation to the RendererConfig interface.

media/mojo/services/renderer_config.h

 // 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.
 
 #ifndef MEDIA_MOJO_SERVICES_RENDERER_CONFIG_H_
 #define MEDIA_MOJO_SERVICES_RENDERER_CONFIG_H_
 
 #include "base/lazy_instance.h"
 #include "base/memory/scoped_vector.h"
 #include "base/single_thread_task_runner.h"
 #include "media/base/audio_decoder.h"
 #include "media/base/audio_hardware_config.h"
 #include "media/base/audio_renderer_sink.h"
 #include "media/base/media_log.h"
 
 namespace media {
 
+// Interface class which clients will extend to override (at compile time) the
+// default audio or video rendering configurations for MojoRendererService.
 class PlatformRendererConfig {
  public:
   virtual ~PlatformRendererConfig() {};
 
+  // The list of audio decoders for use with the AudioRenderer.  Ownership of
+  // the decoders is passed to the caller.  The methods on each decoder will
+  // only be called on |media_task_runner|.  |media_log_cb| should be used to
+  // log errors or important status information.
   virtual ScopedVector<AudioDecoder> GetAudioDecoders(
       const scoped_refptr<base::SingleThreadTaskRunner>& media_task_runner,
       const LogCB& media_log_cb) = 0;
+
+  // The audio output sink used for rendering audio.
   virtual scoped_refptr<AudioRendererSink> GetAudioRendererSink() = 0;
+
+  // The platform's audio hardware configuration.  Note, this must remain
+  // constant for the lifetime of the PlatformRendererConfig.
   virtual const AudioHardwareConfig& GetAudioHardwareConfig() = 0;
+
+  // TODO(dalecurtis): Expose methods for retrieving the video decoders.
 };
 
 class RendererConfig {
  public:
+  // Returns an instance of the RenderConfig object.  Only one instance will
+  // exist per process.
   static RendererConfig* Get();
 
+  // Copy of the PlatformRendererConfig interface.
   ScopedVector<AudioDecoder> GetAudioDecoders(
       const scoped_refptr<base::SingleThreadTaskRunner>& media_task_runner,
       const LogCB& media_log_cb);
   scoped_refptr<AudioRendererSink> GetAudioRendererSink();
   const AudioHardwareConfig& GetAudioHardwareConfig();
 
  private:
   friend struct base::DefaultLazyInstanceTraits<RendererConfig>;
 
   RendererConfig();
   ~RendererConfig();
 
   scoped_ptr<PlatformRendererConfig> renderer_config_;
 
   DISALLOW_COPY_AND_ASSIGN(RendererConfig);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_MOJO_SERVICES_RENDERER_CONFIG_H_