Bug 256193

Summary:	Assert that the scrolling tree is valid, and fix issues with negative z-index layers
Product:	WebKit	Reporter:	Simon Fraser (smfr) <simon.fraser>
Component:	Scrolling	Assignee:	Simon Fraser (smfr) <simon.fraser>
Status:	RESOLVED FIXED
Severity:	Normal	CC:	simon.fraser, webkit-bug-importer
Priority:	P2	Keywords:	InRadar
Version:	WebKit Local Build
Hardware:	Unspecified
OS:	Unspecified
See Also:	https://bugs.webkit.org/show_bug.cgi?id=256195

Description Simon Fraser (smfr) 2023-05-01 20:38:11 PDT

We need to assert in the web process that a committed scrolling tree is valid, which will make it easier to track down causes of MESSAGE_CHECKs related to invalid scrolling trees.

Comment 1 Radar WebKit Bug Importer 2023-05-01 20:38:41 PDT

<rdar://problem/108769471>

Comment 2 Simon Fraser (smfr) 2023-05-01 20:49:25 PDT

Pull request: https://github.com/WebKit/WebKit/pull/13350

Comment 3 EWS 2023-05-02 21:48:16 PDT

Committed 263620@main (46572d8428cb): <https://commits.webkit.org/263620@main>

Reviewed commits have been landed. Closing PR #13350 and removing active labels.