Bug 1950081 [wpt PR 50904] - [carousel] Fix AttachLayoutTree for ::scroll-marker expecting parent, a=testonly

Automatic update from web-platform-tests
[carousel] Fix AttachLayoutTree for ::scroll-marker expecting parent

If ::scroll-marker is inside the element that requires style recalc,
but not layout, context.parent is nullptr. So, we have to if()
attachment instead of CHECK(context.parent).

Fixed: 394980089
Change-Id: Iefdc99a1b65cabeb91d1cf5d7f79e47a0a787e0a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6298048
Reviewed-by: Rune Lillesveen <futharkchromium.org>
Commit-Queue: Daniil Sakhapov <sakhapovchromium.org>
Cr-Commit-Position: refs/heads/main{#1423840}

--

wpt-commits: 6f1558a74c6ef1f52085a594cae98744b260ef6a
wpt-pr: 50904

UltraBlame original commit: 9b6078b98032a8fbabcad6c77474a42a55b3f01e

Author: marco-c

testing/web-platform/tests/css/css-overflow/scroll-markers-inside-canvas-crash.html

@@ -0,0 +1,96 @@
+<
+!
+DOCTYPE
+html
+>
+<
+link
+rel
+=
+"
+help
+"
+href
+=
+"
+crbug
+.
+com
+/
+394980089
+"
+>
+<
+style
+>
+#
+scroller
+{
+overflow
+:
+scroll
+;
+scroll
+-
+marker
+-
+group
+:
+after
+;
+}
+#
+item
+:
+:
+scroll
+-
+marker
+{
+content
+:
+"
+X
+"
+}
+<
+/
+style
+>
+<
+div
+id
+=
+"
+scroller
+"
+>
+<
+canvas
+>
+<
+div
+id
+=
+"
+item
+"
+>
+You
+don
+'
+t
+see
+me
+<
+/
+div
+>
+<
+/
+canvas
+>
+<
+/
+div
+>

testing/web-platform/tests/css/css-overflow/scroll-markers-inside-select-crash.html

@@ -0,0 +1,88 @@
+<
+!
+DOCTYPE
+html
+>
+<
+link
+rel
+=
+"
+help
+"
+href
+=
+"
+crbug
+.
+com
+/
+394980089
+"
+>
+<
+style
+>
+#
+scroller
+{
+overflow
+:
+scroll
+;
+scroll
+-
+marker
+-
+group
+:
+after
+;
+}
+#
+scroller
+div
+:
+:
+scroll
+-
+marker
+{
+content
+:
+counter
+(
+test
+)
+;
+}
+<
+/
+style
+>
+<
+select
+>
+<
+div
+id
+=
+"
+scroller
+"
+>
+<
+div
+>
+<
+/
+div
+>
+<
+/
+div
+>
+<
+/
+select
+>