All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=823051

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=9a64e98b47e0cf47515ea7fddb8d823eb92be8caf07bc176735a163e4549be2f


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

android-nexus5
android-nexus6
android-nexus7v2

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/14a87ed1440000

📍 Found significant differences after each of 2 commits.
https://pinpoint-dot-chromeperf.appspot.com/job/14a87ed1440000

[esnext] Implement Array.prototype.{flatten,flatMap} 🥙 by mathias@chromium.org
https://chromium.googlesource.com/v8/v8/+/697d39abff90510523f297bb8577d5c64322229f

Update WritableStream to latest standard version by ricea@chromium.org
https://chromium.googlesource.com/chromium/src/+/22f1175d58878e0da74589453bc64f264d4679c8

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

The WritableStream-related regression is almost certainly issue 759519. There used to be a way to see what other metrics moved at the same time, but I can't find it now.

There's a small possibility the test page in question is actually using Streams, in which case this would be a real issue. Is there any way to grep the Javascript that the test runs?