[css-grid-1] Static position is resolved against content box like every other display type. Fixes #3020.

Author: tabatkins

css-display-3/Overview.bs

@@ -24,11 +24,8 @@ At Risk: All multi-keyword values of 'display'
 </pre>
 <pre class="link-defaults">
 spec:css-break-3; type:dfn; text:fragment;
-spec:css22;
+spec:css2;
 	type:property; text:overflow;
-	type:dfn;
-		text: table wrapper box
-		text: table box
 spec: html;
 	type: dfn; text: rendered legend
 	type: element; text: a
@@ -91,7 +88,7 @@ Introduction</h2>
 	but when the element generates multiple boxes,
 	are sometimes defined to apply to a different box:
 	for example, the 'border' properties applied to a table element
-	are applied to its <a>table box</a>,
+	are applied to its <a>table grid box</a>,
 	not to its <a lt="principal box">principal</a> <a>table wrapper box</a>.
 	If the value computation process alters the styles of those boxes,
 	and the element's style is requested
@@ -297,11 +294,11 @@ Box Layout Modes: the 'display' property</h2>
 			<tr>
 				<td>''table''
 				<td>''block table''
-				<td><a>block-level</a> <a>table wrapper box</a> containing <a>table box</a>
+				<td><a>block-level</a> <a>table wrapper box</a> containing <a>table grid box</a>
 			<tr>
 				<td>''inline-table''
 				<td>''inline table''
-				<td><a>inline-level</a> <a>table wrapper box</a> containing <a>table box</a>
+				<td><a>inline-level</a> <a>table wrapper box</a> containing <a>table grid box</a>
 		<tbody title="Layout-internal display types">
 			<!--
 			<tr>
@@ -404,7 +401,7 @@ Inner Display Layout Models: the ''flow'', ''flow-root'', ''table'', ''flex'', '
 			The element generates a principal <a>table wrapper box</a>
 			that establishes a <a>block formatting context</a>,
 			and which contains
-			an additionally-generated <a>table box</a>
+			an additionally-generated <a>table grid box</a>
 			that establishes a <a>table formatting context</a>. [[!CSS2]]
 
 		<dt><dfn>flex</dfn>
@@ -468,7 +465,7 @@ Layout-Internal Display Types: the ''table-*'' and ''ruby-*'' keywords</h3>
 
 	The <<display-internal>> keywords are defined as follows:
 
-	<dl dfn-type=value dfn-for="display, <display-internal>">
+	<dl export dfn-type=value dfn-for="display, <display-internal>">
 		<dt><dfn>table-row-group</dfn>, <dfn>table-header-group</dfn>, <dfn>table-footer-group</dfn>, <dfn>table-row</dfn>, <dfn>table-cell</dfn>, <dfn>table-column-group</dfn>, <dfn>table-column</dfn>
 		<dd>
 			The element is an <dfn dfn for>internal table element</dfn>.
@@ -885,7 +882,7 @@ Appendix A: Glossary</h2>
 			which generate an additional marker box,
 			or ''display/table'' elements,
 			which generate a [=principal box|principal=] [=table wrapper box=]
-			and an additional [=table box=]).
+			and an additional [=table grid box=]).
 			These additional boxes are placed with respect to the principal box.
 
 		<dt><dfn lt="inline-level|inline-level content">inline-level</dfn>

css-grid-1/Overview.bs

@@ -3257,7 +3257,7 @@ With a Grid Container as Parent</h3>
 	of an absolutely-positioned child of a <a>grid container</a>
 	is determined as if it were the sole grid item
 	in a <a>grid area</a>
-	whose edges coincide with the padding edges of the <a>grid container</a>.
+	whose edges coincide with the content edges of the <a>grid container</a>.
 	However, if the <a>grid container</a> parent is also the generator of the absolutely positioned element's <a>containing block</a>,
 	instead use the <a>grid area</a> determined in [[#abspos-items]].
 
@@ -4442,6 +4442,18 @@ Major Changes</h4>
         <li id="change-2018-line-name-auto">
             Exclude 'auto' from line name <<custom-ident>>.
             (<a href="https://github.com/w3c/csswg-drafts/issues/2856">Issue 2856</a>)
+
+        <li id="change-2018-static-padding">
+		The static position of a grid container child
+		should be resolved against the content edge, not padding edge, of the grid container.
+		(<a href="https://github.com/w3c/csswg-drafts/issues/3020">Issue 3020</a>)
+		<blockquote>
+			<p>The <a href="https://www.w3.org/TR/CSS21/visudet.html#abs-non-replaced-width">static position</a> [[!CSS21]]
+				of an absolutely-positioned child of a <a>grid container</a>
+				is determined as if it were the sole grid item
+				in a <a>grid area</a>
+				whose edges coincide with the <del>padding</del> <ins>content</ins> edges of the <a>grid container</a>.
+		</blockquote>
 	</ul>
 
 <h4 id="clarify-2017">