Make CSSInterpolationType::maybeConvertSingle() final

third_party/WebKit/Source/core/animation/CSSInterpolationType.h

Index: third_party/WebKit/Source/core/animation/CSSInterpolationType.h
diff --git a/third_party/WebKit/Source/core/animation/CSSInterpolationType.h b/third_party/WebKit/Source/core/animation/CSSInterpolationType.h
index a9553a1ac7154b0f8107a455a0497c0a0a2aa75f..1094c973a2fe2c8f4df7734e7ca096ab8a39ab1a 100644
--- a/third_party/WebKit/Source/core/animation/CSSInterpolationType.h
+++ b/third_party/WebKit/Source/core/animation/CSSInterpolationType.h
@@ -19,7 +19,7 @@ class CSSInterpolationType : public InterpolationType {
   InterpolationValue maybeConvertSingle(const PropertySpecificKeyframe&,
                                         const InterpolationEnvironment&,
                                         const InterpolationValue& underlying,
-                                        ConversionCheckers&) const override;
+                                        ConversionCheckers&) const final;
   virtual InterpolationValue maybeConvertNeutral(
       const InterpolationValue& underlying,
       ConversionCheckers&) const = 0;
@@ -30,6 +30,7 @@ class CSSInterpolationType : public InterpolationType {
   virtual InterpolationValue maybeConvertValue(const CSSValue&,
                                                const StyleResolverState&,
                                                ConversionCheckers&) const = 0;
+  virtual void additiveKeyframeHook(InterpolationValue&) const {}
 
   InterpolationValue maybeConvertUnderlyingValue(
       const InterpolationEnvironment&) const final;
@@ -42,6 +43,13 @@ class CSSInterpolationType : public InterpolationType {
   virtual void applyStandardPropertyValue(const InterpolableValue&,
                                           const NonInterpolableValue*,
                                           StyleResolverState&) const = 0;
+
+ private:
+  InterpolationValue maybeConvertSingleInternal(
+      const PropertySpecificKeyframe&,
+      const InterpolationEnvironment&,
+      const InterpolationValue& underlying,
+      ConversionCheckers&) const;
 };
 
 }  // namespace blink