Web Animations: Split image slice interpolation out of LengthBoxStyleInterpolation

Source/core/animation/StringKeyframe.cpp

Index: Source/core/animation/StringKeyframe.cpp
diff --git a/Source/core/animation/StringKeyframe.cpp b/Source/core/animation/StringKeyframe.cpp
index d07256024591e614f497dd83b1624a98a77e3ee6..51961faf6b623c15059e90c89334fdafdf128374 100644
--- a/Source/core/animation/StringKeyframe.cpp
+++ b/Source/core/animation/StringKeyframe.cpp
@@ -10,6 +10,7 @@
 #include "core/animation/ConstantStyleInterpolation.h"
 #include "core/animation/DeferredLegacyStyleInterpolation.h"
 #include "core/animation/DoubleStyleInterpolation.h"
+#include "core/animation/ImageSliceStyleInterpolation.h"
 #include "core/animation/ImageStyleInterpolation.h"
 #include "core/animation/LegacyStyleInterpolation.h"
 #include "core/animation/LengthBoxStyleInterpolation.h"
@@ -320,9 +321,7 @@ PassRefPtrWillBeRawPtr<Interpolation> StringKeyframe::PropertySpecificKeyframe::
 
     }
 
-    case CSSPropertyClip:
-    case CSSPropertyBorderImageSlice:
-    case CSSPropertyWebkitMaskBoxImageSlice: {
+    case CSSPropertyClip: {
         if (LengthBoxStyleInterpolation::usesDefaultInterpolation(*fromCSSValue, *toCSSValue)) {
             forceDefaultInterpolation = true;
             break;
@@ -333,6 +332,17 @@ PassRefPtrWillBeRawPtr<Interpolation> StringKeyframe::PropertySpecificKeyframe::
         break;
     }
 
+    case CSSPropertyBorderImageSlice:
+    case CSSPropertyWebkitMaskBoxImageSlice: {
+        RefPtrWillBeRawPtr<Interpolation> interpolation = ImageSliceStyleInterpolation::maybeCreate(*fromCSSValue, *toCSSValue, property);
+        if (interpolation)
+            return interpolation.release();
+        if (ImageSliceStyleInterpolation::usesDefaultInterpolation(*fromCSSValue, *toCSSValue))
+            forceDefaultInterpolation = true;
+
+        break;
+    }
+
     case CSSPropertyStrokeWidth: {
         RefPtrWillBeRawPtr<Interpolation> interpolation = SVGLengthStyleInterpolation::maybeCreate(*fromCSSValue, *toCSSValue, property, RangeNonNegative);
         if (interpolation)