Fix behaviour of shadow interpolation with mismatched list lengths

third_party/WebKit/Source/core/animation/CSSShadowListInterpolationType.cpp

Index: third_party/WebKit/Source/core/animation/CSSShadowListInterpolationType.cpp
diff --git a/third_party/WebKit/Source/core/animation/CSSShadowListInterpolationType.cpp b/third_party/WebKit/Source/core/animation/CSSShadowListInterpolationType.cpp
index 4ae5e64d56d16aee3c1720f4f387b8d52e27e843..e78a955f96615234261e930cf9190629b068b385 100644
--- a/third_party/WebKit/Source/core/animation/CSSShadowListInterpolationType.cpp
+++ b/third_party/WebKit/Source/core/animation/CSSShadowListInterpolationType.cpp
@@ -116,6 +116,7 @@ PairwiseInterpolationValue CSSShadowListInterpolationType::MaybeMergeSingles(
     InterpolationValue&& end) const {
   return ListInterpolationFunctions::MaybeMergeSingles(
       std::move(start), std::move(end),
+      ListInterpolationFunctions::kPadToLargest,
       ShadowInterpolationFunctions::MaybeMergeSingles);
 }
 
@@ -134,6 +135,7 @@ void CSSShadowListInterpolationType::Composite(
     double interpolation_fraction) const {
   ListInterpolationFunctions::Composite(
       underlying_value_owner, underlying_fraction, *this, value,
+      ListInterpolationFunctions::kPadToLargest,
       ShadowInterpolationFunctions::NonInterpolableValuesAreCompatible,
       ShadowInterpolationFunctions::Composite);
 }