--- a/dom/animation/EffectSet.h
+++ b/dom/animation/EffectSet.h
@@ -156,16 +156,18 @@ public:
   Iterator begin() { return Iterator(*this); }
   Iterator end() { return Iterator::EndIterator(*this); }
 #ifdef DEBUG
   bool IsBeingEnumerated() const { return mActiveIterators != 0; }
 #endif
 
   bool IsEmpty() const { return mEffects.IsEmpty(); }
 
+  size_t Count() const { return mEffects.Count(); }
+
   RefPtr<AnimValuesStyleRule>& AnimationRule(EffectCompositor::CascadeLevel
                                              aCascadeLevel)
   {
     return mAnimationRule[aCascadeLevel];
   }
 
   const TimeStamp& AnimationRuleRefreshTime(EffectCompositor::CascadeLevel
                                               aCascadeLevel) const