Add VP9 to chrome_webrtc_perf_browsertest.cc.

60 sec audio-video call ->

60 sec audio-video call VP8
60 sec audio-video call VP9
60 sec audio-video call Default

BUG=chromium:554512

Review URL: https://codereview.chromium.org/1755073002

Cr-Commit-Position: refs/heads/master@{#379537}
3 files changed