Allow CastContentBrowserClient to customise media pipeline device

chromecast/media/cma/backend/media_pipeline_device.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 CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_PIPELINE_DEVICE_H_
 #define CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_PIPELINE_DEVICE_H_
 
+#include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace chromecast {
 namespace media {
 class AudioPipelineDevice;
 class MediaClockDevice;
 class MediaPipelineDeviceParams;
 class VideoPipelineDevice;
 
 // MediaPipelineDevice is the owner of the underlying audio/video/clock
 // devices.
 class MediaPipelineDevice {
  public:
   MediaPipelineDevice();
   virtual ~MediaPipelineDevice();
 
   virtual AudioPipelineDevice* GetAudioPipelineDevice() const = 0;
 
   virtual VideoPipelineDevice* GetVideoPipelineDevice() const = 0;
 
   virtual MediaClockDevice* GetMediaClockDevice() const = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MediaPipelineDevice);
 };
 
-// Factory to create a MediaPipelineDevice.
+// Factory method to create a MediaPipelineDevice.
+typedef base::Callback<scoped_ptr<MediaPipelineDevice>(
+    const MediaPipelineDeviceParams&)> CreatePipelineDeviceCB;
+
+// Direct creation of vendor-specific media device pipeline.
+// TODO(halliwell): move into libcast_media
 scoped_ptr<MediaPipelineDevice> CreateMediaPipelineDevice(
     const MediaPipelineDeviceParams& params);
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_PIPELINE_DEVICE_H_