commit 8e4234fdc272ddda5ec9c156a2397c64d7a69f60
author Chris Harrelson <chrishtr@chromium.org> Fri Mar 02 23:51:16 2018
committer Commit Bot <commit-bot@chromium.org> Fri Mar 02 23:51:16 2018
tree b3379aec4565eab2df74885f06ef0a95a3ed0105
parent c7056ddb3e81ad2e9a1fdd8fe48c6b65d400153b

[RLS] Don't include composited scroll offset in squashing offset from transformed ancestor.

Squashed layers determine their position within the squashing layer backing by trampolining
through their transformed ancestor. Currently the scroll offset of this ancestor is included
(including for the LayoutView if RLS is on), but this is not necessary, as the offsets
up and down the layout tree cancel each other.

This change should not have any user-visible or bugfix impact by itself, but will
unblock no longer updating compositing state on root scroll.

Also changed callsites to all use the pre-computed TransformAncestor method rather than
a PaintLayer tree walk.

Bug:814615

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I5b59333f8ae33123a6f74f83ce0c7d0cc78f33fc
Reviewed-on: https://chromium-review.googlesource.com/946560
Reviewed-by: vmpstr <vmpstr@chromium.org>
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540687}