Philipp Hancke 3ea9fc4cd8 Make frame transformer MimeType pure virtual again
after both audio and video have been implemented.

BUG=webrtc:15579

Change-Id: Ib52e8f67292259cbf7497a884672de72f3003282
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/326162
Commit-Queue: Philipp Hancke <phancke@microsoft.com>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Tony Herre <herre@google.com>
Cr-Commit-Position: refs/heads/main@{#41114}
2023-11-09 12:28:10 +00:00
..
2023-03-21 16:54:19 +00:00