The SW and HW encoder have separate picture id sequences. Set picture id to not cause sequence discontinuties at encoder changes. Bug: webrtc:6634 Change-Id: Ie47168791399303d88cbec3ef6ae8ef8c16ced30 Reviewed-on: https://webrtc-review.googlesource.com/5481 Commit-Queue: Stefan Holmer <stefan@webrtc.org> Reviewed-by: Stefan Holmer <stefan@webrtc.org> Reviewed-by: Rasmus Brandt <brandtr@webrtc.org> Cr-Commit-Position: refs/heads/master@{#20188}