1695089 - [wpt-sync] Sync PR 27792 - Never force legacy layout on NG objects.

Status: RESOLVED FIXED

(Core :: Layout, task, P4)

Description

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Sync web-platform-tests PR 27792 into mozilla-central (this bug is closed when the sync is complete).

PR: https://github.com/web-platform-tests/wpt/pull/27792
Details from upstream follow.

b'Morten Stenshorne <[e-mail]>' wrote:

Never force legacy layout on NG objects.

Remove dangerous legacy fallback code from LayoutObject(), and do this
safely in the child insertion code instead.

Calling a virtual method in a base class constructor doesn't work.
IsLayoutNGObject() would always return false, since that's how it's
implemented in LayoutObject. This code could cause us to mark an NG
object as requiring legacy fallback, which would make the NG engine
delegate the job to the legacy engine. But the legacy engine would
refuse to do anything, since it's an NG object, so it would delegate to
NG, and so on... Infinite recursion.

The !IsLayoutNGObject() check in LayoutObject() was a mistake added in
CL:2414289, which basically had no effect at all. But we can just remove
the entire thing now, and rely on the new hook in the child insertion
code instead.

Note that the new test doesn't fail without this fix when run normally
by the test runner, because the test needs LayoutNGTextControl to be
disabled in order to fail (so that we attempt legacy fallback), but this
feature is currently set to "test". Unlike the fuzzer, it seems...

Bug: 1181687
Change-Id: I2f174824e4b86d9ae2e5b3b319df7f6036b4f13d

Reviewed-on: https://chromium-review.googlesource.com/2720104
WPT-Export-Revision: bdc73f85894056cb8bf8086da7ef7a673a5dffd7

Comment 1

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Pushed to try (stability) https://treeherder.mozilla.org/#/jobs?repo=try&revision=4061612280dd1319fdc2ce9d4da56e5f56642db7

Comment 2

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

CI Results

Ran 14 Firefox configurations based on mozilla-central, and Firefox, Chrome, and Safari on GitHub CI

Total 1 tests

Status Summary

Firefox

PASS : 1

Chrome

CRASH: 1

Safari

PASS : 1

Links

Gecko CI (Treeherder)
GitHub PR Head
GitHub PR Base

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5b8c457acc17
[wpt PR 27792] - Never force legacy layout on NG objects., a=testonly

Comment 4

[Dorel Luca [:dluca]]

https://hg.mozilla.org/mozilla-central/rev/5b8c457acc17