So that third party projects don't still have to implement it when they
switch over to the new signature.
Bug: webrtc:8473
Change-Id: I329814ad6e899def7bad97939e8643380a268f91
Reviewed-on: https://webrtc-review.googlesource.com/26022
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20885}