All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=872172

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=c207525c50ece037c06bfcde827bbcb018258a2686d38fd306f407dddd4ec8b2


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

Android Nexus6 WebView Perf

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/12e74778640000

📍 Found a significant difference after 1 commit.
https://pinpoint-dot-chromeperf.appspot.com/job/12e74778640000

Only invalidate property trees and compositing for PaintLayers when needed, on style change. by chrishtr@chromium.org
https://chromium.googlesource.com/chromium/src/+/ba8c87a1a32815e6061b7c38d31ddfbbaac7a124
15.25 → 18.49 (+3.244)

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

The regressions appear to all be on mobile WebViews.

My first theory after perusing the patch is that in cases where
PaintLayer::AttemptDirectCompositingUpdate returned true, which
previously avoided SetNeedsCompositingInputsUpdate() in PaintLayer::StyleDidChange.

Now we may be able to have SetNeedsCompositingInputsUpdate happen in some of these
cases. I think the code in LayoutObject::StyleDidChange in my patch might trigger 
in this case.

If so, this is a real regression since the whole point of AttemptDirectCompositingUpdate
is to provide a fast path for composited transform and opacity animations.

 Issue 872596  has been merged into this issue.

 Issue 873382  has been merged into this issue.

 Issue 874874  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/82efd6c5c86089eda2d54a0783e429ff96a36825

commit 82efd6c5c86089eda2d54a0783e429ff96a36825
Author: Chris Harrelson <chrishtr@chromium.org>
Date: Tue Aug 21 20:45:52 2018

Reduce over-invalidation of compositing inputs.

In particular, for cases when the PaintLayer direct compositing update fast-path
applies.

Bug:  872172 

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: If059f2f76d9973c2a19d2f326f495e4891813d6e
Reviewed-on: https://chromium-review.googlesource.com/1171797
Reviewed-by: vmpstr <vmpstr@chromium.org>
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584892}
[modify] https://crrev.com/82efd6c5c86089eda2d54a0783e429ff96a36825/third_party/blink/renderer/core/layout/layout_object.cc
[modify] https://crrev.com/82efd6c5c86089eda2d54a0783e429ff96a36825/third_party/blink/renderer/core/paint/paint_layer.cc

Two regressions are now resolved. Two remain:

https://chromeperf.appspot.com/group_report?bug_id=874874
https://chromeperf.appspot.com/group_report?bug_id=873382

 Issue 875981  has been merged into this issue.

I think this was caused by an over-invalidation in LayoutView when it
recomputes overflow. If overflow did not actually change, compositing inputs
don't need to be dirtied.

Fixed in:

https://chromium.googlesource.com/chromium/src/+/d1042cc805130a5ed959f06593787dd0021106dc

Will request merge after verifying bots recover.

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Recovered.

Your change meets the bar and is auto-approved for M70. Please go ahead and merge the CL to branch 3538 manually. Please contact milestone owner if you have questions.
Owners: benmason@(Android), kariahda@(iOS), geohsu@(ChromeOS), abdulsyed@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

https://chromium.googlesource.com/chromium/src/+/557dccd0a078ffd17d77f832b8affa23d965e596

This issue has been approved for a merge. Please merge the fix to any appropriate branches as soon as possible!

If all merges have been completed, please remove any remaining Merge-Approved labels from this issue.

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already merged.