[css-grid] Static position should use content-box, not padding-box #3020
Description
Tab and I just noticed that while every other layout mode uses the content box of the static position containing block to set the static position, grid uses the padding box.
We suspect this was an error and we should fix this. Anyone have a different opinion?
Spec: https://drafts.csswg.org/css-grid-1/#static-position
Testcase: http://software.hixie.ch/utilities/js/live-dom-viewer/saved/6105
<!DOCTYPE html>
<style>
.abspos { position: absolute; border: 4px solid rgba(0,0,0,.4) }
.container { float: left; border: solid; padding: 2em; width: 10em; height: 6em; background: yellow content-box }
</style>
<div class=container style="display: grid;"><span class=abspos></span>grid</div>
<div class=container style="display: flex;"><span class=abspos></span>flex</div>
<div class=container style="display: block;"><span class=abspos></span>block</div>