[cssom][css-conditional] Merge IDL definitions for CSSMediaRule (#1209)

Fixes #851.

Author: zcorpan

css-conditional/Overview.bs

@@ -927,18 +927,18 @@ interface CSSConditionRule : CSSGroupingRule {
 <h3 id="the-cssmediarule-interface">
 The <code>CSSMediaRule</code> interface</h3>
 
-<p>The {{CSSMediaRule}} interface represents a ''@media'' rule:
+<p>The {{CSSMediaRule}} interface represents a ''@media'' at-rule:
 
 <pre class='idl'>
 interface CSSMediaRule : CSSConditionRule {
-    readonly attribute <a href="https://www.w3.org/TR/DOM-Level-2-Style/stylesheets.html#StyleSheets-MediaList">MediaList</a> media;
+    [SameObject, PutForwards=mediaText] readonly attribute MediaList media;
 };
 </pre>
 
 <dl class='idl-attributes'>
-  <dt><code>media</code> of type <code><a href="https://www.w3.org/TR/DOM-Level-2-Style/stylesheets.html#StyleSheets-MediaList">MediaList</a></code>, readonly
-  <dd>The <code>media</code> attribute must return a <code>MediaList</code> object
-    for the list of media queries specified with the ''@media'' rule.
+  <dt><code>media</code> of type {{MediaList}}, readonly
+  <dd>The <code>media</code> attribute must return a {{MediaList}} object
+    for the list of media queries specified with the ''@media'' at-rule.
 
   <dt><code>conditionText</code> of type <code>CSSOMString</code> (CSSMediaRule-specific definition for attribute on CSSConditionRule)
   <dd>The <code>conditionText</code> attribute (defined on the <code>CSSConditionRule</code> parent rule),

cssom/Overview.bs

@@ -1732,16 +1732,8 @@ The <dfn method for=CSSGroupingRule>deleteRule(<var>index</var>)</dfn> method mu
 
 ### The {{CSSMediaRule}} Interface ### {#the-cssmediarule-interface}
 
-The <code>CSSMediaRule</code> interface represents an <code>@media</code> at-rule.
-
-<pre class=idl>
-interface CSSMediaRule : CSSGroupingRule {
-  [SameObject, PutForwards=mediaText] readonly attribute MediaList media;
-};
-</pre>
-
-The <dfn attribute for=CSSGroupingRule>media</dfn> attribute must return a <code>MediaList</code> object for the list of media queries specified
-with the <code>@media</code> at-rule.
+The {{CSSMediaRule}} interface is defined in <cite>CSS Conditional Rules</cite>.
+[[!CSS3-CONDITIONAL]]
 
 
 ### The {{CSSPageRule}} Interface ### {#the-csspagerule-interface}