[css-conditional-4] Move definition of @supports selector to css-conditional-4.

Author: emilio

css-conditional-3/Overview.bs

@@ -245,9 +245,8 @@ with <<supports-condition>> defined as:
 	                     | <<supports-in-parens>> [ and <<supports-in-parens>> ]*
 	                     | <<supports-in-parens>> [ or <<supports-in-parens>> ]*
 	<dfn>&lt;supports-in-parens></dfn> = ( <<supports-condition>> ) | <<supports-feature>> | <<general-enclosed>>
-	<dfn>&lt;supports-feature></dfn> = <<supports-selector-fn>> | <<supports-decl>>
+	<dfn>&lt;supports-feature></dfn> = <<supports-decl>>
 	<dfn>&lt;supports-decl></dfn> = ( <<declaration>> )
-	<dfn>&lt;supports-selector-fn></dfn> = selector( <<complex-selector>> )
 </pre>
 
 The above grammar is purposely very loose for forwards-compatibility reasons,
@@ -287,12 +286,6 @@ as follows:
 ::
 	The result is true if the UA [=supports=] the declaration within the parentheses.
 
-: <<supports-selector-fn>>
-::
-	The result is true if the UA
-	<a href="#dfn-support-selector">supports the selector</a>
-	provided as an argument to the function.
-
 : <<general-enclosed>>
 ::
 	The result is unknown.
@@ -479,12 +472,6 @@ compound values; implementations must implement all parts of the value
 in order to consider the declaration supported, either inside a style rule
 or in the declaration condition of an ''@supports'' rule.
 
-A CSS processor is considered to
-<dfn export for=CSS id="dfn-support-selector">support a CSS selector</dfn>
-if it accepts that selector (rather than discarding it as a
-parse error), and that selector doesn't contain
-<a>unknown -webkit- pseudo-elements</a>.
-
 <h2 id="apis">APIs</h2>
 
 <h3 id='extentions-to-cssrule-interface'>

css-conditional-4/Overview.bs

@@ -27,6 +27,28 @@ and have not yet been copied here.
 
 Issue: In the future, copy the contents of [[css3-conditional]] into this document.
 
+<h2 id="at-supports-ext">Extensions to the ''@supports'' rule</h2>
+
+This level of the specification extends the <<supports-feature>> syntax as follows:
+
+<pre class="prod def" nohighlight>
+	<dfn>&lt;supports-feature></dfn> = <<supports-selector-fn>> | <<supports-decl>>
+	<dfn>&lt;supports-selector-fn></dfn> = selector( <<complex-selector>> )
+</pre>
+
+: <<supports-selector-fn>>
+::
+	The result is true if the UA
+	<a href="#dfn-support-selector">supports the selector</a>
+	provided as an argument to the function.
+
+<h3 id="support-definition-ext">Extensions to the definition of support</h3>
+
+A CSS processor is considered to
+<dfn export for=CSS id="dfn-support-selector">support a CSS selector</dfn>
+if it accepts that selector (rather than discarding it as a
+parse error), and that selector doesn't contain
+<a>unknown -webkit- pseudo-elements</a>.
 
 <h2 class=no-num id="acknowledgments">Acknowledgments</h2>