Introduce BorderImageLength and BorderImageLengthBox

Source/core/rendering/RenderBoxModelObject.cpp

Index: Source/core/rendering/RenderBoxModelObject.cpp
diff --git a/Source/core/rendering/RenderBoxModelObject.cpp b/Source/core/rendering/RenderBoxModelObject.cpp
index 072a4cfce33699283c81cfc7dc0389d869201c0a..91fbba82da3d68608e5ce861d9b97062c4e5bc93 100644
--- a/Source/core/rendering/RenderBoxModelObject.cpp
+++ b/Source/core/rendering/RenderBoxModelObject.cpp
@@ -1148,13 +1148,13 @@ void RenderBoxModelObject::calculateBackgroundImageGeometry(const FillLayer* fil
     geometry.setDestOrigin(geometry.destRect().location());
 }
 
-static LayoutUnit computeBorderImageSide(Length borderSlice, LayoutUnit borderSide, LayoutUnit imageSide, LayoutUnit boxExtent, RenderView* renderView)
+static LayoutUnit computeBorderImageSide(const BorderImageLength& borderSlice, LayoutUnit borderSide, LayoutUnit imageSide, LayoutUnit boxExtent, RenderView* renderView)
 {
-    if (borderSlice.isRelative())
-        return borderSlice.value() * borderSide;
-    if (borderSlice.isAuto())
+    if (borderSlice.isNumber())
+        return borderSlice.number() * borderSide;
+    if (borderSlice.length().isAuto())
         return imageSide;
-    return valueForLength(borderSlice, boxExtent, renderView);
+    return valueForLength(borderSlice.length(), boxExtent, renderView);
 }
 
 bool RenderBoxModelObject::paintNinePieceImage(GraphicsContext* graphicsContext, const LayoutRect& rect, const RenderStyle* style,