1847730 - [wpt-sync] Sync PR 41382 - Fix a DCHECK with “will-change: contents” on partial MPC hits.

Status: RESOLVED FIXED

(Core :: Layout, task, P4)

Description

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

Sync web-platform-tests PR 41382 into mozilla-central (this bug is closed when the sync is complete).

PR: https://github.com/web-platform-tests/wpt/pull/41382
Details from upstream follow.

Steinar H. Gunderson <[e-mail]> wrote:

Fix a DCHECK with “will-change: contents” on partial MPC hits.

This was probably a long-standing issue that was only recently uncovered
with the added DCHECKs that things came out right after a partial MPC hit.
The issue is that we relied on setting will-change (which was marked as
noninherited) to set WillChangeContentsSubtree (which was marked as
inherited). So if we got a partial MPC hit, we would copy over all
noninherited properties from the MPC entry, and skip applying will-change.
But the inherited property WillChangeContentsSubtree would not get
copied, and also, nothing would set it (it would stay at its initial
value of false, inherited from the parent), and thus, it would be the
wrong value.

We now do this pseudo-inheritance with yet another hack in StyleAdjuster
instead.

Bug: 1469858, 1470253, 1470406, 1470689

Change-Id: I124c943148fa2a97fd7d969616d3fb15562f70b4

Reviewed-on: https://chromium-review.googlesource.com/4754284
WPT-Export-Revision: 306ffe66314a58cea691429d561b1f3a9432bada

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=259586dd7332fce3f9e522a27fd9fd15d3edb015

Comment 2

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

CI Results

Ran 9 Firefox configurations based on mozilla-central, and Firefox, Chrome, and Safari on GitHub CI

Total 1 tests

Status Summary

Firefox

PASS: 1

Chrome

PASS: 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/92946265f33a
[wpt PR 41382] - Fix a DCHECK with “will-change: contents” on partial MPC hits., a=testonly

Comment 4

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/92946265f33a