Fixed incorrect handling of timestamps in video quality test
Fixed incorrect handling of timestamps in video quality test

* Both timestamps must be unwrapped before comparing
* rtp timestamp delta must be subtracted before unwrapping

BUG=webrtc:5637, webrtc:5537

Review URL: https://codereview.webrtc.org/1774123003

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#11926}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 16daaa5a407e0b7c6918ee0974d1b00c5a7f0db3

jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk