--- a/layout/style/nsStyleStruct.h
+++ b/layout/style/nsStyleStruct.h
@@ -2255,21 +2255,16 @@ struct StyleTransition
   // Delay and Duration are in milliseconds
 
   const nsTimingFunction& GetTimingFunction() const { return mTimingFunction; }
   float GetDelay() const { return mDelay; }
   float GetDuration() const { return mDuration; }
   nsCSSPropertyID GetProperty() const { return mProperty; }
   nsAtom* GetUnknownProperty() const { return mUnknownProperty; }
 
-  float GetCombinedDuration() const {
-    // http://dev.w3.org/csswg/css-transitions/#combined-duration
-    return std::max(mDuration, 0.0f) + mDelay;
-  }
-
   void SetTimingFunction(const nsTimingFunction& aTimingFunction)
     { mTimingFunction = aTimingFunction; }
   void SetDelay(float aDelay) { mDelay = aDelay; }
   void SetDuration(float aDuration) { mDuration = aDuration; }
   void SetProperty(nsCSSPropertyID aProperty)
     {
       NS_ASSERTION(aProperty != eCSSProperty_UNKNOWN &&
                    aProperty != eCSSPropertyExtra_variable,