[Mojo Video Capture] Retire buffers when Android Chromium goes to the background

media/capture/video/video_frame_receiver.h

 // Copyright 2016 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_CAPTURE_VIDEO_VIDEO_FRAME_RECEIVER_H_
 #define MEDIA_CAPTURE_VIDEO_VIDEO_FRAME_RECEIVER_H_
 
 #include "media/capture/capture_export.h"
 #include "media/capture/video/video_capture_device.h"
 
 namespace media {
 
 // Callback interface for VideoCaptureDeviceClient to communicate with its
 // clients.
 class CAPTURE_EXPORT VideoFrameReceiver {
  public:
   virtual ~VideoFrameReceiver(){};
 
   virtual void OnIncomingCapturedVideoFrame(
       media::VideoCaptureDevice::Client::Buffer buffer,
       scoped_refptr<media::VideoFrame> frame) = 0;
   virtual void OnError() = 0;
   virtual void OnLog(const std::string& message) = 0;
-  virtual void OnBufferDestroyed(int buffer_id_to_drop) = 0;
+
+  // Tells the VideoFrameReceiver that the producer is no longer going to use
+  // the buffer with id |buffer_id| for frame delivery. This may be called even
+  // while the receiver is still consuming the buffer from a call to
+  // OnIncomingCapturedVideoFrame(). In that case, it means that the
+  // caller is asking the VideoFrameReceiver to release the buffer
+  // at its earliest convenience.
+  // A producer may reuse a retired |buffer_id| immediately after this call.
+  virtual void OnBufferRetired(int buffer_id) = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_CAPTURE_VIDEO_VIDEO_FRAME_RECEIVER_H_