This CL updates the file and class naming, based on the naming discussion in
https://webrtc-review.googlesource.com/c/src/+/265877.
Concretely, that means replacing "delta" with "variation" in the name.
Bug: webrtc:14151
Change-Id: I43e74b1d25f9441015445101f3eb6a7b52f3adba
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/273960
Commit-Queue: Rasmus Brandt <brandtr@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37999}
665875b0d8