Fix AV sync logspam

This VLOG(2) should really be VLOG(3), as VLOG(2) is enabled by default
for us and it's quite a lot of logs.

BUG= b/109897412
TEST=None

Change-Id: Ia5c132e7dabb584e51442d0234e1bf814c37ae76
Reviewed-on: https://chromium-review.googlesource.com/1092158Reviewed-by: Sergey Volk <servolk@chromium.org>
Commit-Queue: Mina Almasry <almasrymina@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565511}

chromecast/media/cma/backend/video/av_sync_video.cc

@@ -146,7 +146,7 @@ void AvSyncVideo::UpkeepAvSync() {
   int64_t difference;
   error_->EstimateY(now, &difference, &error);
 
-  VLOG(2) << "Pts_monitor."
+  VLOG(3) << "Pts_monitor."
           << " difference=" << difference / 1000 << " apts_slope=" << apts_slope
           << " apts_slope=" << apts_slope
           << " current_audio_playback_rate_=" << current_audio_playback_rate_