--- a/dom/webidl/KeyframeEffect.webidl
+++ b/dom/webidl/KeyframeEffect.webidl
@@ -41,20 +41,28 @@ interface KeyframeEffectReadOnly : Anima
   // KeyframeEffect             clone();
 
   // We use object instead of ComputedKeyframe so that we can put the
   // property-value pairs on the object.
   [Throws] sequence<object> getFrames();
 };
 
 // Non-standard extensions
+dictionary AnimationPropertyValueDetails {
+  double             offset;
+  DOMString          value;
+  DOMString          easing;
+  CompositeOperation composite;
+};
+
 dictionary AnimationPropertyDetails {
-  DOMString  property;
-  boolean    runningOnCompositor;
-  DOMString? warning;
+  DOMString                               property;
+  boolean                                 runningOnCompositor;
+  DOMString?                              warning;
+  sequence<AnimationPropertyValueDetails> values;
 };
 
 partial interface KeyframeEffectReadOnly {
   [ChromeOnly] sequence<AnimationPropertyDetails> getProperties();
 };
 
 [Func="nsDocument::IsWebAnimationsEnabled",
  Constructor ((Element or CSSPseudoElement)? target,