--- a/dom/webidl/CSSStyleDeclaration.webidl
+++ b/dom/webidl/CSSStyleDeclaration.webidl
@@ -22,14 +22,8 @@ interface CSSStyleDeclaration {
   DOMString getPropertyPriority(DOMString property);
   [CEReactions, Throws]
   void setProperty(DOMString property, [TreatNullAs=EmptyString] DOMString value, [TreatNullAs=EmptyString] optional DOMString priority = "");
   [CEReactions, Throws]
   DOMString removeProperty(DOMString property);
 
   readonly attribute CSSRule? parentRule;
 };
-
-// Mozilla extensions
-partial interface CSSStyleDeclaration {
-  [ChromeOnly,Throws]
-  DOMString getAuthoredPropertyValue(DOMString property);
-};