Insert first packet before calling to decode.
Bug: webrtc:10690
Change-Id: I721b7af0506f0dbaf4fa2ed6a9ba6a87250d08f1
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/139103
Reviewed-by: Minyue Li <minyue@webrtc.org>
Commit-Queue: Pablo Barrera González <barrerap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28149}