This is a preparation for inheriting the method from the base class,
and delete the corresponding redundant timestamp member.
TBR: magjed@webrtc.org
Bug: webrtc:9378
Change-Id: I27a0ec83fb20ac3da58ba32b86cf794a154deca0
Reviewed-on: https://webrtc-review.googlesource.com/83123
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23594}