Wire up BitrateAllocation to be sent as RTCP TargetBitrate

webrtc/common_video/include/video_bitrate_allocator.h

Index: webrtc/common_video/include/video_bitrate_allocator.h
diff --git a/webrtc/common_video/include/video_bitrate_allocator.h b/webrtc/common_video/include/video_bitrate_allocator.h
index 66ff077be5b06441692f23fdadcaa885f5ac9448..b85879db4b52daf1f165d7051d420e7c66a30fb5 100644
--- a/webrtc/common_video/include/video_bitrate_allocator.h
+++ b/webrtc/common_video/include/video_bitrate_allocator.h
@@ -25,6 +25,15 @@ class VideoBitrateAllocator {
   virtual uint32_t GetPreferredBitrateBps(uint32_t framerate) = 0;
 };
 
+class VideoBitrateAllocationObserver {
+ public:
+  VideoBitrateAllocationObserver() {}
+  virtual ~VideoBitrateAllocationObserver() {}
+
+  virtual void OnBitrateAllocationUpdated(
+      const BitrateAllocation& allocation) = 0;
+};
+
 }  // namespace webrtc
 
 #endif  // WEBRTC_COMMON_VIDEO_INCLUDE_VIDEO_BITRATE_ALLOCATOR_H_