Add test for verifying configured key frame interval for VP9.

BUG=

Review URL: https://codereview.webrtc.org/1498053002

Cr-Original-Commit-Position: refs/heads/master@{#11004}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 38bb8ad1ca93d28d6f0055bb5663dff95d82a1e8
1 file changed