All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=830767

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=66dc4bf1b5a4bd66f1ad02c3a5ad6271346823d46da9ce2ac40a44373975e87e


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

android-nexus5
android-nexus6
android-nexus7v2
android-one
chromium-rel-mac11-pro
chromium-rel-mac12
chromium-rel-win10
chromium-rel-win7-dual
chromium-rel-win7-gpu-ati
chromium-rel-win7-gpu-intel
chromium-rel-win7-gpu-nvidia
chromium-rel-win7-x64-dual
chromium-rel-win8-dual
linux-release

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/14f05f4cc40000

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/12a101e3c40000

📍 Found significant differences after each of 7 commits.
https://pinpoint-dot-chromeperf.appspot.com/job/12a101e3c40000

Fix nullptr crash in UpdateSubFrameScrollOnMainReason by bokan@chromium.org
https://chromium.googlesource.com/chromium/src/+/e9b22fae0b577b224dc99e33ad573afe84a2ad97

Reduce usage of |caret_offset| in AdjustInlineBoxPositionForTextDirectionInternal by xiaochengh@chromium.org
https://chromium.googlesource.com/chromium/src/+/099a01702350aafe8525b28b58d7e74359fafaba

<b>Fix frame lifecycle for UI<->WebVR handoff</b> by klausw@chromium.org
https://chromium.googlesource.com/chromium/src/+/dbff879cf3e9f62d055433c8f664003a58c99aec

Remove debugging line. by apacible@chromium.org
https://chromium.googlesource.com/chromium/src/+/72e902e08a324735bf7222f9d980616a183b9eaf

Fix a crash in debug build due to invalidate weakptr on wrong thread by bshe@chromium.org
https://chromium.googlesource.com/chromium/src/+/8460d1bc090aed56b86845e7f3501a6d38d04f4f

[RLS] Do not use scrollbar-excluded overflow clip at the root by pdr@chromium.org
https://chromium.googlesource.com/chromium/src/+/86d1cc1b33260b95367afdedb6195c842dc8e5c0

Move STHDistributor, STHObserver, and STHReporter out of //net by rsleevi@chromium.org
https://chromium.googlesource.com/chromium/src/+/6d00e4f36107c15910509a7766debb81921e5993

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

This was just moving files around, so... assigning back to primiano.

I don't see how this could be the "Fix frame lifecycle for UI<->WebVR handoff" change, that code is only active for VR Browsing and WebVR on Android. The files it changed are not part of the build for Mac/Win/Linux.

This looks like my bug. I'm not sure why it wasn't duped automatically.