[css-pseudo] Add ::inactive-selection pseudo per WG resolution

Author: fantasai

css-pseudo/Overview.bs

@@ -423,28 +423,31 @@ Styling the ''::first-letter'' Pseudo-element</h4>
 Highlight Pseudo-elements</h2>
 
 <h3 id="highlight-selectors">
-Selecting Highlighted Content: the ''::selection'', ''::spelling-error'', and ''::grammar-error'' pseudo-elements</h3>
+Selecting Highlighted Content: the ''::selection'',  ''::inactive-selection'', ''::spelling-error'', and ''::grammar-error'' pseudo-elements</h3>
 
   The <dfn>highlight pseudo-elements</dfn>
   represent portions of a document that have been highlighted in some way.
 
   <dl export>
     <dt><dfn>::selection</dfn>
+    <dt><dfn>::inactive-selection</dfn>
     <dd>
-      The <a>::selection</a> pseudo-element represents
+      The ''::selection'' and ''::inactive-selection'' pseudo-elements represent
       the portion of a document that has been highlighted by the user.
       This also applies, for example, to selected text within an editable text field.
 
-      Issue: Active vs. inactive selections are often styled differently. Currently no way to distinguish.
+      ''::selection'' applies to active selections,
+      wherease ''::inactive-selection'' applies to inactive selections
+      (e.g. when the document window is inactive and therefore not receiving events).
 
     <dt><dfn>::spelling-error</dfn>
     <dd>
-      The <a>::spelling-error</a> pseudo-element represents
+      The ''::spelling-error'' pseudo-element represents
       a portion of text that has been flagged by the user agent as misspelled.
 
     <dt><dfn>::grammar-error</dfn>
     <dd>
-      The <a>::grammar-error</a> pseudo-element represents
+      The ''::grammar-error'' pseudo-element represents
       a portion of text that has been flagged by the user agent as grammatically incorrect.
   </dl>
 
@@ -915,6 +918,7 @@ Changes</h2>
   <ul>
     <li>Addition of the ''::marker'' pseudo-element.
     <li>Removed special handling of floated ''::first-letter'' in favor of <a href="https://www.w3.org/TR/css-inline-3/#initial-letter-styling">initial letter styling</a>. [[CSS-INLINE-3]]
+    <li>Added ''::inactive-selection''.
     <li>Defined handling of text decorations on ''::selection'' to match IE's more sensible behavior.
     <li>Links to pseudo-element OM design discussions.
     <li>Various minor clarifications.