The stable target rate is used to make smarter choices in the rate to chose which layers to enable in SVC or simulcast modes. the addition of hysteresis, we can improve a call quality by reducing the amount of resolution switch. Bug: webrtc:10126 Change-Id: I04d0df9e6bbe247e2f2a668207ff74d475e2464c Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/150642 Reviewed-by: Niels Moller <nisse@webrtc.org> Reviewed-by: Erik Språng <sprang@webrtc.org> Commit-Queue: Florent Castelli <orphis@webrtc.org> Cr-Commit-Position: refs/heads/master@{#29112}