to allow writing DependencyDescriptor value that is not copiable. and avoid copying RtpGenericFrameDescriptor Bug: webrtc:10342 Change-Id: I6eefa9d06b90d7e858f224443ba6769975b556fe Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/166171 Reviewed-by: Markus Handell <handellm@webrtc.org> Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/master@{#30322}