Removing the redundant last_estimated_bitrate_bps_ and renaming some members to better reflect the contents. Also replacing the CurrentEstimate method of SendSideBandwidthEstimation with value specific access methods. Bug: webrtc:9883 Change-Id: I73cb08e09374adddf5991cb3793fa4a4fee20c85 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/154351 Reviewed-by: Niels Moller <nisse@webrtc.org> Commit-Queue: Sebastian Jansson <srte@webrtc.org> Cr-Commit-Position: refs/heads/master@{#29304}