The original cl broke some downstream project because some internal source
encoders do not call OnBitrateChanged on GenericEncoder.
Bug: webrtc:9058
Change-Id: I7841c65059fb4fc9e1ab9754bb1d232ce660a990
Reviewed-on: https://webrtc-review.googlesource.com/66342
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22733}