Bug 312190 – [iOS release] compositing/accelerated-layers-after-back-2.html is a flaky image diff

• Status: NEW
• Component: New Bugs

[Diego De La Toba]

Created attachment 479051 [details]
diff-compositing/accelerated-layers-after-back-2

compositing/accelerated-layers-after-back-2.html is a flaky image diff on iOS release.


HISTORY:
https://results.webkit.org/?suite=layout-tests&test=compositing%2Faccelerated-layers-after-back-2.html


IMAGE URL:
https://build.webkit.org/results/Apple-iOS-26-Simulator-Release-WK2-Tests/311091%40main%20(2578)/compositing/accelerated-layers-after-back-2-diffs.html


IMAGES:
SEE ATTACHED. 


REPRODUCTION:
I was able to reproduce this failure on iOS 26.4 with the following:

run-webkit-tests --no-build --no-retry --no-show-results --exit-after-n-failures=1 --expect-pass --iterations=1000 --force --ios-simulator --release compositing/accelerated-layers-after-back-2.html

I am going to mark expectations imageOnlyFailure and pass.

[Radar WebKit Bug Importer]

<rdar://problem/174686610>

[Diego De La Toba]

Test gardening pull request: https://github.com/WebKit/WebKit/pull/62669

[EWS]

Test gardening commit 311140@main (613955c00be7): <https://commits.webkit.org/311140@main>

Reviewed commits have been landed. Closing PR #62669 and removing active labels.

[Diego De La Toba]

The flake in this test is resolved by swapping the order in which we add elements to the page, (i.e swapping line 24 and 25). With the current implementation, the link is added after a container of 2000px is added, forcing a scroll to verify the link is present (flake happens here). Swapping the order resolves the flake but suggests an issue with how rendering is handled with scrolling. While it fixes the flake it suggests an underlying issue with WebKit.