Trigger on total bitrate change. Bug: webrtc:8955 Change-Id: I2373a1b7f139c7ea748a9641593e714d6895c8f6 Reviewed-on: https://webrtc-review.googlesource.com/59323 Reviewed-by: Stefan Holmer <stefan@webrtc.org> Reviewed-by: Sebastian Jansson <srte@webrtc.org> Commit-Queue: Philip Eliasson <philipel@webrtc.org> Cr-Commit-Position: refs/heads/master@{#22323}