[mediaqueries] Be more explicit about what kinds of things can affects MQs.

Author: tabatkins

mediaqueries/Overview.html

@@ -281,7 +281,8 @@ <h2 class="heading settled heading" data-level=2 id=media><span class=secno>2 </
 	its styling,
 	or any other internal aspect;
 	they’re only dependent on “external” information
-	unless otherwise specified.
+	unless another feature explicitly specifies that it affects the resolution of Media Queries,
+	such as the <span class=css data-link-type=maybe title=@viewport>@viewport</span> rule.
 
 <p>	The syntax of a <a data-link-type=dfn href=#media-query title="media query">media query</a> consists of
 	an optional <a data-link-type=dfn href=#media-query-modifier title="media query modifier">media query modifier</a>,

mediaqueries/Overview.src.html

@@ -131,7 +131,8 @@ <h2 id="media">
 	its styling,
 	or any other internal aspect;
 	they're only dependent on “external” information
-	unless otherwise specified.
+	unless another feature explicitly specifies that it affects the resolution of Media Queries,
+	such as the ''@viewport'' rule.
 
 	The syntax of a <a>media query</a> consists of
 	an optional <a>media query modifier</a>,