[selectors] Actually define the specificifity of :matches() properly.

Author: tabatkins

selectors/Overview.html

@@ -3919,12 +3919,15 @@ <h2 id=specificity><span class=secno>15. </span> Calculating a selector's
   </ul>
 
   <p>The specificity of a <a href="#matches">:matches()</a> pseudo-class is
-   the specificity of its most specific argument. The specificity of a <a
-   href="#negation">:negation()</a> pseudo-class is the maximum specificity
-   of any of its component selectors. In either case, the pseudo-class itself
-   does not contribute any additional specificity. For example,
-   <code>:matches(em, strong)</code> has a specificity of (0,0,1), like a tag
-   selector.
+   the specificity of the most specific complex selector that matched. (The
+   full selector's specificity is equivalent to expanding out all the
+   combinations in full, without <a
+   href="#matches-pseudo"><code>:matches()</code></a>.) The specificity of a
+   <a href="#negation">:not()</a> pseudo-class is the specificity of the most
+   specifc complex selector in its selector list. In either case, the
+   pseudo-class itself does not contribute any additional specificity. For
+   example, <code>:matches(em, strong)</code> has a specificity of (0,0,1),
+   like a tag selector.
 
   <p> Specificities are compared by comparing the three components in order:
    the specificity with a larger <var>a</var> value is more specific; if the

selectors/Overview.src.html

@@ -2842,9 +2842,10 @@ <h2 id="specificity">
   </ul>
 
   <p>The specificity of a <a href="#matches">:matches()</a> pseudo-class is 
-    the specificity of its most specific argument. 
-    The specificity of a <a href="#negation">:negation()</a> pseudo-class is
-    the maximum specificity of any of its component selectors.
+    the specificity of the most specific complex selector that matched.
+    (The full selector's specificity is equivalent to expanding out all the combinations in full, without <code>:matches()</code>.)
+    The specificity of a <a href="#negation">:not()</a> pseudo-class is
+    the specificity of the most specifc complex selector in its selector list.
     In either case, the pseudo-class itself does not contribute any additional specificity.
     For example, <code>:matches(em, strong)</code> has a specificity of (0,0,1), like a tag selector.