Adjust css-view-transitions/span-with-overflowing-text-and-box-decorations.html to use a 20px font-size (divisible by 5) for its Ahem text

[dholbert]

Test List

https://wpt.fyi/results/css/css-view-transitions/span-with-overflowing-text-and-box-decorations.html

Rationale

This test is currently annotated as having lots of fuzzy pixels:

<meta name="fuzzy" content="maxDifference=0-3;totalPixels=0-4900">

...and it currently has a slightly-worse-than-allowed fuzzy failure in Firefox, as shown on wpt.fyi.

Rather than bumping the threshold to get Firefox passing, I looked at why the test is fuzzy, and (in Firefox at least) it's because it uses an Ahem font-size of 12px:

:root {
  font: 12px/1 Ahem;
}

That goes against two general recommendations for using Ahem in WPTs -- quoting with numbers added by me for readability:

1. If the test uses the Ahem font, make sure its computed font-size is a multiple of 5px, otherwise baseline alignment may be rendered inconsistently.
2. A minimum computed font-size of 20px is suggested.

https://web-platform-tests.org/writing-tests/ahem.html#usage

If I switch to 20px/1 Ahem to satisfy those recommendations, then the test passes in Firefox with no fuzzy pixels (I assume in other browsers as well).

I propose we make that change.

[dholbert]

I submitted a PR with the test change (and the fuzzy tolerance meta-tag removed, since I think it'll no longer be needed).

Test results will show up at some point later today at this URL, I think:
https://wpt.fyi/results/css/css-view-transitions/span-with-overflowing-text-and-box-decorations.html?sha=c9524bb&label=pr_head&max-count=1

[dholbert]

@khushalsagar you're the test-author here - does this seem OK to you?

(And maybe @nt1m can review for WebKit?)

[dholbert]

(looks like I do need to preserve the fuzzy annotation for Chromium and WebKit to continue passing, so I'll update the PR to keep that)

[dholbert]

This will soon have test results with the fuzzy annotation restored:
https://wpt.fyi/results/css/css-view-transitions/span-with-overflowing-text-and-box-decorations.html?sha=3e30521&label=pr_head&max-count=1

[nt1m]

Looks ok for Blink (given @noamr's approval) & WebKit.