Fix behaviour of shadow interpolation with mismatched list lengths

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

Index: third_party/WebKit/Source/core/animation/ListInterpolationFunctions.h
diff --git a/third_party/WebKit/Source/core/animation/ListInterpolationFunctions.h b/third_party/WebKit/Source/core/animation/ListInterpolationFunctions.h
index 8e1fe604b7deaf49dd15b20c68dac0df3d4f0933..9e868cbfb0b7a5e312516f52e6b8fab385d8fdc1 100644
--- a/third_party/WebKit/Source/core/animation/ListInterpolationFunctions.h
+++ b/third_party/WebKit/Source/core/animation/ListInterpolationFunctions.h
@@ -23,12 +23,15 @@ class ListInterpolationFunctions {
     return InterpolationValue(InterpolableList::Create(0));
   }
 
+  enum class LengthMatchingStrategy { kLowestCommonMultiple, kPadToLargest };
+
   using MergeSingleItemConversionsCallback =
       PairwiseInterpolationValue (*)(InterpolationValue&& start,
                                      InterpolationValue&& end);
   static PairwiseInterpolationValue MaybeMergeSingles(
       InterpolationValue&& start,
       InterpolationValue&& end,
+      LengthMatchingStrategy,
       MergeSingleItemConversionsCallback);
 
   using EqualNonInterpolableValuesCallback =
@@ -48,6 +51,7 @@ class ListInterpolationFunctions {
                         double underlying_fraction,
                         const InterpolationType&,
                         const InterpolationValue&,
+                        LengthMatchingStrategy,
                         NonInterpolableValuesAreCompatibleCallback,
                         CompositeItemCallback);
 };