commit 119bdd8cf87b8a391f743c349fa12cbc00833148
author David Bokan <bokan@chromium.org> Fri Dec 15 15:37:19 2023
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Fri Dec 15 15:37:19 2023
tree c4d8416661d7968f5980bdf7ca09594ad7e46310
parent be65c57f8c273deafabbc8a03c55d08a3968caed

vt: Fix CHECK trying to merge anonymous block

This CHECK would trip as changing listStylePosition triggers a layout
tree reattachment[1]. This causes the documentElement's LayoutObject to
be removed which happens before the LayoutViewTransitionRoot.

LayoutViewTransitionRoot represents the snapshot containing block and
doesn't have an associated Node, making it "anonymous".

When documentElement's object is removed, it removes itself from the
parent LayoutView. Since LayoutViewTransitionRoot is the only remaining
child, LayoutView tries to hoist its contents onto itself in
CollapseAnonymousBlockChild[2] since anonymous blocks are typically
created artificially to host non-block content in a block flow. This
tries to add the ::view-transition LayoutObject to LayoutView which
trips the CHECK that LayoutView doesn't yet have a
LayoutViewTransitionRoot, since doing so will add one.

LayoutViewTransitionRoot is anonymous but doesn't want to have this
merging/collapsing property so this CL opts it out of that behavior.

[1] https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/style/computed_style.cc;l=372;drc=a9187270cee16e9adf8ba3b0286ab80694448a70
[2] https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/layout/layout_block_flow.cc;l=271;drc=0e6e802410c16813e03bd2884f8e7f7889b87783

Bug: 1505249
Change-Id: Ifcd2e3b0e54fe9bc84a741142196031ad566c626
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5122373
Commit-Queue: David Bokan <bokan@chromium.org>
Reviewed-by: Vladimir Levin <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1238076}