[selectors] Define that :active propagates to ancestors, and that host languages can define more ways to match :active.

Author: tabatkins

selectors/Overview.bs

@@ -2151,7 +2151,7 @@ The pointer hover pseudo-class '':hover''</h3>
 	(e.g., a pen device that does not detect hovering)
 	are still conforming.
 
-	The parent of an element that is '':hover'' is also in that state.
+	The parent of an element that matches '':hover'' also matches '':hover''.
 
 	Note: When an element that is '':hover'' is in a <a>shadow tree</a>,
 	the <a>host element</a> (and its parents) are also in the '':hover'' state. (See [[css-scoping-1]])
@@ -2181,8 +2181,9 @@ The activation pseudo-class '':active''</h3>
 	which elements can become '':active''.
 	For example, [[HTML5]] defines a <a href="http://www.whatwg.org/html/selectors.html#selector-active">list of activatable elements</a>.
 
-	Selectors doesn't define if the parent of an element that is
-	':active' is also in that state.
+	The parent of an element that matches '':active'' also matches '':active''.
+
+	Host languages may define additional ways in which an element can match '':active''.
 
 	Note: An element can be both
 	':visited' and ':active' (or ':link' and ':active').

selectors/Overview.html

@@ -2385,7 +2385,7 @@ <h3 class="heading settled" data-level=9.1 id=the-hover-pseudo><span class=secno
 	(e.g., a pen device that does not detect hovering)
 	are still conforming.</p>
 
-<p>The parent of an element that is <a class=css data-link-type=maybe href=#hover-pseudo title=:hover>:hover</a> is also in that state.</p>
+<p>The parent of an element that matches <a class=css data-link-type=maybe href=#hover-pseudo title=:hover>:hover</a> also matches <a class=css data-link-type=maybe href=#hover-pseudo title=:hover>:hover</a>.</p>
 
 <p class=note role=note>Note: When an element that is <a class=css data-link-type=maybe href=#hover-pseudo title=:hover>:hover</a> is in a <a data-link-type=dfn href=http://dev.w3.org/csswg/css-scoping-1/#shadow-tree title="shadow tree">shadow tree</a>,
 	the <a data-link-type=dfn href=http://dev.w3.org/csswg/css-scoping-1/#host-element0 title="host element">host element</a> (and its parents) are also in the <a class=css data-link-type=maybe href=#hover-pseudo title=:hover>:hover</a> state. (See <a data-biblio-type=informative data-link-type=biblio href=#biblio-css-scoping-1 title=css-scoping-1>[css-scoping-1]</a>)</p>
@@ -2415,8 +2415,9 @@ <h3 class="heading settled" data-level=9.2 id=the-active-pseudo><span class=secn
 	which elements can become <a class=css data-link-type=maybe href=#active-pseudo title=:active>:active</a>.
 	For example, <a data-biblio-type=informative data-link-type=biblio href=#biblio-html5 title=HTML5>[HTML5]</a> defines a <a href=http://www.whatwg.org/html/selectors.html#selector-active>list of activatable elements</a>.</p>
 
-<p>Selectors doesn’t define if the parent of an element that is
-	':active' is also in that state.</p>
+<p>The parent of an element that matches <a class=css data-link-type=maybe href=#active-pseudo title=:active>:active</a> also matches <a class=css data-link-type=maybe href=#active-pseudo title=:active>:active</a>.</p>
+
+<p>Host languages may define additional ways in which an element can match <a class=css data-link-type=maybe href=#active-pseudo title=:active>:active</a>.</p>
 
 <p class=note role=note>Note: An element can be both
 	':visited' and ':active' (or ':link' and ':active').</p>