Add test for dropping repeated NTP timestamps.

Regression test for enforcing that frames with repeated or old NTP
timestamps are dropped.

BUG=chromium:480953, webrtc:4615
R=stefan@webrtc.org

Review URL: https://codereview.webrtc.org/1220193002

Cr-Commit-Position: refs/heads/master@{#9533}
1 file changed