Add test for dropping repeated NTP timestamps.

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

Committed: https://crrev.com/db0cf7624e8b7782e8b0864f9e01925ecdc3027d
Cr-Commit-Position: refs/heads/master@{#9533}

[pbos-webrtc, 2015-07-02 09:43:00]

PTAL, the bug said to do it all the way to the encoder, but I don't think that's
necessary, this is the part responsible for dropping duplicate input and all
frames should go through it.

[pbos-webrtc, 2015-07-02 09:43:06]

The CQ bit was checked by pbos@webrtc.org to run a CQ dry run

[commit-bot: I haz the power, 2015-07-02 09:43:18]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1220193002/1

[stefan-webrtc, 2015-07-02 09:45:39]

lgtm

[pbos-webrtc, 2015-07-02 11:00:03]

The CQ bit was checked by pbos@webrtc.org

[pbos-webrtc, 2015-07-02 11:00:03]

The CQ bit was unchecked by pbos@webrtc.org

[pbos-webrtc, 2015-07-02 11:00:10]

The CQ bit was checked by pbos@webrtc.org

[commit-bot: I haz the power, 2015-07-02 11:00:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1220193002/1

[commit-bot: I haz the power, 2015-07-02 11:14:51]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-02 11:15:02]

Patchset 1 (id:??) landed as
https://crrev.com/db0cf7624e8b7782e8b0864f9e01925ecdc3027d
Cr-Commit-Position: refs/heads/master@{#9533}