render_time time field (means capture time for sender side) is used by rtcp SenderReport to calculate offset since last frame and to estimate rtp timestamp for the time SenderReport should be send at.
mapping between rtp timestamp and ntp time in SenderReport is used for stream synchronization.
calculation of rtp_timestamp (using ntp_time of incoming video frame) for rtp packets is unchanged.
BUG=webrtc:5433, webrtc:5504, webrtc:5505
Review URL: https://codereview.webrtc.org/1693443002
Cr-Commit-Position: refs/heads/master@{#11820}