Merge pull request w3c#2573 from saschanaz/patch-1

[css-pseudo-4] EventTarget is not a mixin

Author: tabatkins

css-pseudo-4/Overview.bs

@@ -869,13 +869,11 @@ Interface CSSPseudoElement</h3>
 
   <pre class="idl">
     [Exposed=Window]
-    interface CSSPseudoElement {
+    interface CSSPseudoElement : EventTarget {
         readonly attribute CSSOMString <a href="#dom-csspseudochild-type">type</a>;
         readonly attribute Element element;
         readonly attribute <a href="https://www.w3.org/TR/DOM-Level-2-Style/css.html#CSS-CSSStyleDeclaration">CSSStyleDeclaration</a> <a href="#dom-csspseudochild-style">style</a>;
     };
-
-    CSSPseudoElement implements EventTarget;
   </pre>
 
   The <dfn attribute for=CSSPseudoElement>type</dfn> attribute