Reason for revert:
Multiple definitions of TestEstimator
Original issue's description:
> Pass arrival time as an int64_t rather than a double to the MedianSlopeEstimator to avoid precision loss.
>
> Also clean up the unit test.
>
> BUG=webrtc:6892
>
> Committed: https://crrev.com/ebcbcc3b2451f5c4fb07f7b37815bd54f364d057
> Cr-Commit-Position: refs/heads/master@{#15634}
TBR=brandtr@webrtc.org,stefan@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:6892
Review-Url: https://codereview.webrtc.org/2572353003
Cr-Commit-Position: refs/heads/master@{#15635}
0bac07a89b