when rtp header extension is larger than 2^16 bytes Bug: chromium:811613 Change-Id: I05b725d734dd628056d603b596d3523e827ddb54 Reviewed-on: https://webrtc-review.googlesource.com/52345 Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Reviewed-by: Alex Loiko <aleloi@webrtc.org> Cr-Commit-Position: refs/heads/master@{#22003}