All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=830746

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=fa252043e9e00f988ed16d3ea032600a2f83e22643f8b39d66cc82f85d58ea13


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

chromium-rel-win7-dual

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/13a62bf4c40000

Looks like this was caused by:

[RLS] Do not use scrollbar-excluded overflow clip at the root by pdr@chromium.org

Likely a WontFix as it only affects a single microbenchmark on a single platform but over to pdr to verify.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/26e2572987b0e3a147911c1aa26f7f747968cc01

commit 26e2572987b0e3a147911c1aa26f7f747968cc01
Author: Philip Rogers <pdr@chromium.org>
Date: Wed Apr 25 18:03:59 2018

[RLS] Avoid full tree rebuilds on hit testing clip changes

This is a revert of [1] which caused performance regressions. This patch
reimplements a solution that avoids full tree rebuilds when only hit
testing clip values change in the clip tree.

Typically, when property nodes are updated, we force a full tree
rebuild if nodes are created or destroyed, but not if node values are
simply updated. Clip nodes are an exception to this because changing
their values ends up causing a full tree rebuild. The hit testing clip
rect (aka clip_rect_excluding_overlay_scrollbars) is different though,
and does not need to force a full tree rebuild when it changes. This
patch special-cases the hit testing clip rects to avoid a full tree
rebuild. When overlay scrollbars hide or appear, the hit testing
clip values change but a full tree rebuild is not needed.

[1] https://crrev.com/86d1cc1b33260b95367afdedb6195c842dc8e5c0

Bug:  823999 ,  830746 ,  830771 
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I7ab426aaead0c87a1aedf0980648505d82d40215
Reviewed-on: https://chromium-review.googlesource.com/1026941
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553652}
[modify] https://crrev.com/26e2572987b0e3a147911c1aa26f7f747968cc01/third_party/blink/renderer/core/paint/object_paint_properties.h
[modify] https://crrev.com/26e2572987b0e3a147911c1aa26f7f747968cc01/third_party/blink/renderer/core/paint/paint_layer_clipper.cc
[modify] https://crrev.com/26e2572987b0e3a147911c1aa26f7f747968cc01/third_party/blink/renderer/core/paint/paint_property_tree_builder.cc
[modify] https://crrev.com/26e2572987b0e3a147911c1aa26f7f747968cc01/third_party/blink/renderer/core/paint/paint_property_tree_builder_test.cc
[modify] https://crrev.com/26e2572987b0e3a147911c1aa26f7f747968cc01/third_party/blink/renderer/platform/graphics/paint/clip_paint_property_node.h