Update clip-path-polygon-010.html

[progers]

Test List

css/css-masking/clip-path/clip-path-polygon-010.html

Rationale

The spec states:

For elements with associated CSS layout box, the used value for fill-box is content-box and for stroke-box and view-box is border-box.

The test states:

'fill-box' was specified but is not supported for HTML elements. The used value should be 'border-box' for the polygon() function instead.

I think the test is incorrect and the used value should be "content-box". Firefox currently passes this test, while Chromium and Safari fail.

If this test change proposal is accepted, I would like to make the following changes:

1. Update the test's meta to say The used value should be 'content-box' for the polygon() function instead.
2. Update the clip-path value to be polygon(-75px -50%, 50% -25px, 25px 150%, -75px 75px) fill-box which makes the existing reference work (and both Chromium and Safari will now pass).

@nt1m @dholbert

[dholbert]

Seems fine to me; thanks for the heads-up.

Historical note: git blame shows that the test was added 9 years ago, with its current expectation about the used value being border-box.

The spec agreed with it at that point, but it changed 5 years ago to the current text (with content-box as the used value) in w3c/fxtf-drafts@2c7d482

[dholbert]

I filed https://bugzilla.mozilla.org/show_bug.cgi?id=1852323 to update Firefox to pass the (amended) test and match the current spec on this.

[nt1m]

Sure, seems fine by me

[progers]

Thanks everyone! This should be fixed with web-platform-tests/wpt@4dd1803