Move interpolated Length unit types out of InterpolableValue into NonInterpolableValue

Source/core/animation/LengthInterpolationType.h

Index: Source/core/animation/LengthInterpolationType.h
diff --git a/Source/core/animation/LengthInterpolationType.h b/Source/core/animation/LengthInterpolationType.h
index 64bb35204e07624dc496d1599d4ef871e6910a05..be39e037bd67364583dc154405df309b4047c971 100644
--- a/Source/core/animation/LengthInterpolationType.h
+++ b/Source/core/animation/LengthInterpolationType.h
@@ -17,6 +17,7 @@ public:
     LengthInterpolationType(CSSPropertyID);
 
     PassOwnPtr<InterpolationValue> maybeConvertUnderlyingValue(const StyleResolverState&) const final;
+    void composite(UnderlyingValue&, double underlyingFraction, const InterpolationValue&) const final;
     void apply(const InterpolableValue&, const NonInterpolableValue*, StyleResolverState&) const final;
 
 private:
@@ -28,6 +29,8 @@ private:
     PassOwnPtr<InterpolationValue> maybeConvertInherit(const StyleResolverState*, ConversionCheckers&) const final;
     PassOwnPtr<InterpolationValue> maybeConvertValue(const CSSValue&, const StyleResolverState*, ConversionCheckers&) const final;
 
+    PassOwnPtr<PairwisePrimitiveInterpolation> mergeSingleConversions(InterpolationValue&, InterpolationValue&) const final;
+
     const ValueRange m_valueRange;
 };