WebKit export of https://bugs.webkit.org/show_bug.cgi?id=243899

[lilyspiniolas]

WebKit export from bug: [css-ui] Investigate failures in compute-kind-widget-generated

[wpt-pr-bot]

This patch has been exported from WebKit; it will be approved automatically once the downstream patch is r+.

[lilyspiniolas]

There is a browser difference for how getComputedStyles handles background-position. For WebKit and Gecko, getComputedStyles return the longhands background-position-x and background-position-y, while Chrome returns the shorthand background-position. The lack of the longhands means that these styles, which should cause primitive appearance, are applied to the elements on the page despite the fact that the test should only apply styles which don't cause primitive appearance.

[wpt-pr-bot]

The review process for this patch is being conducted in the WebKit project.