[css-grid] Switch to better 'grid' syntax for auto-flowing, per WG resolution.

Author: tabatkins

css-grid/Overview.bs

@@ -2238,7 +2238,8 @@ Grid Definition Shorthand: the 'grid' property</h2>
 	<pre class='propdef'>
 	Name: grid
 	Value: <<'grid-template'>> |
-	Value: <nobr>[ <<'grid-auto-flow'>> [ <<'grid-auto-rows'>> [ / <<'grid-auto-columns'>> ]? ]? ]</nobr>
+	Value: <nobr><<'grid-template-rows'>> / [ auto-flow && dense? ] <<'grid-auto-columns'>>?</nobr> |
+	Value: <nobr>[ auto-flow && dense? ] <<'grid-auto-rows'>>? / <<'grid-template-columns'>></nobr>
 	Initial: see individual properties
 	Applies to: <a>grid containers</a>
 	Inherited: see individual properties
@@ -2260,12 +2261,20 @@ Grid Definition Shorthand: the 'grid' property</h2>
 	beyond what 'grid-template' defines:
 
 	<dl dfn-for=grid dfn-type=value>
-		<dt><dfn id="grid-auto"><<'grid-auto-flow'>> [ <<'grid-auto-rows'>> [ / <<'grid-auto-columns'>> ]? ]?</dfn>
+		<dt><dfn id='grid-s-auto-row'><<'grid-template-rows'>> / [ auto-flow && dense? ] <<'grid-auto-columns'>>?</dfn>
+		<dt><dfn id='grid-s-auto-column'>[ auto-flow && dense? ] <<'grid-auto-rows'>>? / <<'grid-template-columns'>></dfn>
 		<dd>
-			Sets 'grid-auto-flow', 'grid-auto-rows', and 'grid-auto-columns' as specified.
-			If the <<'grid-auto-columns'>> value is omitted,
-			it is set to the value specified for <<'grid-auto-rows'>>.
-			If both are omitted, they are set to their initial values.
+			Sets up auto-flow,
+			by setting the tracks in one axis explicitly
+			(setting either 'grid-template-rows' or 'grid-template-columns' as specified,
+			and setting the other to ''grid-template-rows/none''),
+			and specifying how to auto-repeat the tracks in the other axis
+			(setting either 'grid-auto-rows' or 'grid-auto-columns' as specified,
+			and setting the other to ''grid-auto-rows/auto'').
+			'grid-auto-flow' is also set to either ''row'' or ''column'' accordingly,
+			with ''dense'' if it's specified.
+
+			All other properties are reset to their initial values.
 	</dl>
 
 	Note: Note that you can only specify the explicit <em>or</em> the implicit grid properties in a single 'grid' declaration.