All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=835351

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=7c29cede2fe2c01c2b10b3f1a43f907e7ed14a0b8916783537d6565be017cb5e


Bot(s) for this bug's original alert(s):

android-nexus6

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/1150ba6ec40000

📍 Found a significant difference after 1 commit.
https://pinpoint-dot-chromeperf.appspot.com/job/1150ba6ec40000

Enable MediaCodecVideoDecoder by default. by liberato@chromium.org
https://chromium.googlesource.com/chromium/src/+/b9b132c175fb9ced0dfa2289a94dc3fe89bb3027

Understanding performance regressions:
  http://g.co/ChromePerformanceRegressions

i'll try to repro locally.

looking at all metrics that changed for that revision:

https://chromeperf.appspot.com/group_report?rev=551799

seems like the only things affected were N6 and N7v2, both older devices.

the trace didn't look particularly interesting.  gpu main thread wan't busy, though there was some stuff at startup.  it didn't have media tracing enabled (requested one, waiting for it to finish).