Return a copy of the frames counters to be able to get DVQA stats while it is running. Bug: b/213863770 Change-Id: I04755117cf363e1f160caa11dbe52fb30324fdf5 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/259867 Reviewed-by: Andrey Logvin <landrey@webrtc.org> Commit-Queue: Artem Titov <titovartem@webrtc.org> Cr-Commit-Position: refs/heads/main@{#36638}