--- a/dom/animation/AnimValuesStyleRule.cpp
+++ b/dom/animation/AnimValuesStyleRule.cpp
@@ -78,16 +78,23 @@ AnimValuesStyleRule::AddValue(nsCSSPrope
 {
   MOZ_ASSERT(aProperty != eCSSProperty_UNKNOWN,
              "Unexpected css property");
   mAnimationValues.Put(aProperty, Move(aValue));
   mStyleBits |=
     nsCachedStyleData::GetBitForSID(nsCSSProps::kSIDTable[aProperty]);
 }
 
+bool
+AnimValuesStyleRule::GetValue(nsCSSPropertyID aProperty,
+                              StyleAnimationValue& aValue) const
+{
+  return mAnimationValues.Get(aProperty, &aValue);
+}
+
 #ifdef DEBUG
 void
 AnimValuesStyleRule::List(FILE* out, int32_t aIndent) const
 {
   nsAutoCString str;
   for (int32_t index = aIndent; --index >= 0; ) {
     str.AppendLiteral("  ");
   }

--- a/dom/animation/AnimValuesStyleRule.h
+++ b/dom/animation/AnimValuesStyleRule.h
@@ -40,16 +40,21 @@ public:
   void List(FILE* out = stdout, int32_t aIndent = 0) const override;
 #endif
 
   // For the following functions, it there is already a value for |aProperty| it
   // will be replaced with |aValue|.
   void AddValue(nsCSSPropertyID aProperty, const StyleAnimationValue &aValue);
   void AddValue(nsCSSPropertyID aProperty, StyleAnimationValue&& aValue);
 
+  bool HasValue(nsCSSPropertyID aProperty) const {
+    return mAnimationValues.Contains(aProperty);
+  }
+  bool GetValue(nsCSSPropertyID aProperty, StyleAnimationValue& aValue) const;
+
 private:
   ~AnimValuesStyleRule() {}
 
   nsDataHashtable<nsUint32HashKey, StyleAnimationValue> mAnimationValues;
 
   uint32_t mStyleBits;
 };