Add code path for registered custom properties in CSSInterpolationType

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

Index: third_party/WebKit/Source/core/animation/CSSValueInterpolationType.h
diff --git a/third_party/WebKit/Source/core/animation/CSSValueInterpolationType.h b/third_party/WebKit/Source/core/animation/CSSValueInterpolationType.h
index 5cc8b3b0e51ce1292e17bb442f0bd3fe09f3b887..3e4a465e1ce74d8f87604df991685bab97c09496 100644
--- a/third_party/WebKit/Source/core/animation/CSSValueInterpolationType.h
+++ b/third_party/WebKit/Source/core/animation/CSSValueInterpolationType.h
@@ -55,6 +55,10 @@ class CSSValueInterpolationType : public CSSInterpolationType {
   void applyStandardPropertyValue(const InterpolableValue&,
                                   const NonInterpolableValue*,
                                   StyleResolverState&) const final;
+
+  const CSSValue* createCSSValue(const InterpolableValue&,
+                                 const NonInterpolableValue*,
+                                 const StyleResolverState&) const final;
 };
 
 }  // namespace blink