[css-anchor-position-1] Add position-anchor:normal that depends on position-area. w3c#13067

Author: tabatkins

css-anchor-position-1/Overview.bs

@@ -321,7 +321,7 @@ This property has no effect on [=implicit anchor elements=].
 Note: Since ancestors of the positioned element are checked first,
 there's usually no need to use 'anchor-scope'
 if the desired anchor is an ancestor.
-It's only needed when the desired anchor is somewhere else,
+It's only needed when the desired anchor is not an ancestor,
 or you explicitly want to "hide" an anchor
 from being referenced elsewhere in the page.
 
@@ -497,8 +497,8 @@ Default Anchors: the 'position-anchor' property</h3>
 
 <pre class=propdef>
 Name: position-anchor
-Value: none | auto | <<anchor-name>>
-Initial: none
+Value: normal | none | auto | <<anchor-name>>
+Initial: normal
 Applies to: [=absolutely positioned boxes=]
 Inherited: no
 Animation type: discrete
@@ -510,6 +510,13 @@ and (by default) all [=anchor functions=] applied to this element.
 'position-anchor' is a [=reset-only sub-property=] of 'position'.
 
 <dl dfn-for=position-anchor dfn-type=value>
+	: <dfn>normal</dfn>
+	::
+		If 'position-area' is ''position-area/none'',
+		behaves as ''position-anchor/none''.
+		Otherwise,
+		behaves as ''position-anchor/auto''.
+
 	: <dfn>none</dfn>
 	::
 		The box has no [=default anchor element=].
@@ -525,10 +532,6 @@ and (by default) all [=anchor functions=] applied to this element.
 		is the box's [=default anchor element=].
 </dl>
 
-Issue(#13067): We might want to change the initial value to be slightly more magical,
-auto-choosing between ''position-anchor/none'' and ''position-anchor/auto''
-based on 'position-area' being used or not.
-
 The [=principal box=] of the [=default anchor element=]
 is the box's <dfn>default anchor box</dfn>.