Previously when BitrateControllerImpl::OnDelayBasedBweResult() is
called as result of a probe it was calling
bandwidth_estimation_.SetSendBitrate(), but not
UpdateDelayBasedEstimate(). As result SendSideBandwidthEstimation was
effectively ignoring probe results as it kept the old
delay_based_bitrate_bps_ value, which caps the resulting bitrate.
BUG=webrtc:6332,webrtc:6710
Review-Url: https://codereview.webrtc.org/2481383002
Cr-Commit-Position: refs/heads/master@{#15071}