[css-syntax] Fix bug in the ndashdigit cases, so it retrieves from the ident's representation as appropraite.

Author: tabatkins

css-syntax/Overview.html

@@ -4156,9 +4156,9 @@ <h3 id=the-anb-type><span class=secno>6.2. </span> The <a
     href="#ltdashndashdigit-ident"><code><var>&lt;dashndashdigit-ident></var></code></a>
 
    <dd> <a href="#a"><var>A</var></a> is the dimension's value, 1, or -1,
-    respectively. <a href="#b"><var>B</var></a> is the dimension's unit, with
-    the first two characters removed and the remainder interpreted as a
-    base-10 number.
+    respectively. <a href="#b"><var>B</var></a> is the dimension's unit or
+    ident's representation, as appropriate, with the first two characters
+    removed and the remainder interpreted as a base-10 number.
 
    <dt><code><a href="#ltn-dimension"><var>&lt;n-dimension></var></a> <a
     href="#ltsigned-integer"><var>&lt;signed-integer></var></a></code>

css-syntax/Overview.src.html

@@ -3053,7 +3053,7 @@ <h3 id="the-anb-type">
 		<dt><code>'+'? <var>&lt;ndashdigit-ident></var></code>
 		<dt><code><var>&lt;dashndashdigit-ident></var></code>
 		<dd>
-			<var>A</var> is the dimension's value, 1, or -1, respectively. <var>B</var> is the dimension's unit, with the first two characters removed and the remainder interpreted as a base-10 number.
+			<var>A</var> is the dimension's value, 1, or -1, respectively. <var>B</var> is the dimension's unit or ident's representation, as appropriate, with the first two characters removed and the remainder interpreted as a base-10 number.
 
 		<dt><code><var>&lt;n-dimension></var> <var>&lt;signed-integer></var></code>
 		<dt><code>'+'? n <var>&lt;signed-integer></var></code>