Fix behaviour of shadow interpolation with mismatched list lengths

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/animation/CSSImageListInterpolationType.h"
 
 #include <memory>
 #include "core/animation/CSSImageInterpolationType.h"
 #include "core/animation/ImageListPropertyFunctions.h"
 #include "core/animation/ListInterpolationFunctions.h"
@@ skipping 129 matching lines @@
   return InterpolationValue(
       std::move(interpolable_list),
       NonInterpolableList::Create(std::move(non_interpolable_values)));
 }
 
 PairwiseInterpolationValue CSSImageListInterpolationType::MaybeMergeSingles(
     InterpolationValue&& start,
     InterpolationValue&& end) const {
   return ListInterpolationFunctions::MaybeMergeSingles(
       std::move(start), std::move(end),
+      ListInterpolationFunctions::kLowestCommonMultiple,
       CSSImageInterpolationType::StaticMergeSingleConversions);
 }
 
 InterpolationValue
 CSSImageListInterpolationType::MaybeConvertStandardPropertyUnderlyingValue(
     const ComputedStyle& style) const {
   StyleImageList underlying_image_list;
   ImageListPropertyFunctions::GetImageList(CssProperty(), style,
                                            underlying_image_list);
   return MaybeConvertStyleImageList(underlying_image_list);
@@ skipping 22 matching lines @@
   for (size_t i = 0; i < length; i++) {
     image_list[i] = CSSImageInterpolationType::ResolveStyleImage(
         CssProperty(), *interpolable_list.Get(i), non_interpolable_list.Get(i),
         state);
   }
   ImageListPropertyFunctions::SetImageList(CssProperty(), *state.Style(),
                                            image_list);
 }
 
 }  // namespace blink