Extract bitrate allocation of spatial/temporal layers out of codec impl.

webrtc/common_video/include/video_bitrate_allocator.h

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#ifndef WEBRTC_MODULES_AUDIO_CODING_CODECS_AUDIO_FORMAT_CONVERSION_H_
-#define WEBRTC_MODULES_AUDIO_CODING_CODECS_AUDIO_FORMAT_CONVERSION_H_
+#ifndef WEBRTC_COMMON_VIDEO_INCLUDE_VIDEO_BITRATE_ALLOCATOR_H_
+#define WEBRTC_COMMON_VIDEO_INCLUDE_VIDEO_BITRATE_ALLOCATOR_H_
 
 #include "webrtc/common_types.h"
-#include "webrtc/modules/audio_coding/codecs/audio_format.h"
 
 namespace webrtc {
 
-SdpAudioFormat CodecInstToSdp(const CodecInst& codec_inst);
+class VideoBitrateAllocator {
+ public:
+  VideoBitrateAllocator() {}
+  virtual ~VideoBitrateAllocator() {}
+
+  virtual BitrateAllocation GetAllocation(uint32_t total_bitrate,
+                                          uint32_t framerate) = 0;
+  virtual uint32_t GetPreferedBitrate(int frame_rate) = 0;
+};
 
 }  // namespace webrtc
 
-#endif  // WEBRTC_MODULES_AUDIO_CODING_CODECS_AUDIO_FORMAT_CONVERSION_H_
+#endif  // WEBRTC_COMMON_VIDEO_INCLUDE_VIDEO_BITRATE_ALLOCATOR_H_