Factor out common BorderImageLength code in CSSToStyleMap

Source/build/scripts/templates/StyleBuilderFunctions.cpp.tmpl

 {% from "macros.tmpl" import lower_first -%}
 
 {#
     This file is for property handlers which use the templating engine to
     reduce (handwritten) code duplication.
 
     The `properties' dict can be used to access a property's parameters in
     jinja2 templates (i.e. setter, getter, initial, type_name)
 -#}
 
@@ skipping 159 matching lines @@
 {{ apply_value_border_image("CSSPropertyWebkitBorderImage") }}
 
 {%- macro apply_border_image_modifier(property_id, modifier_type) %}
 {%- set is_mask_box = "MaskBox" in property_id %}
 {%- set getter = "maskBoxImage" if is_mask_box else "borderImage" %}
 {%- set setter = "setMaskBoxImage" if is_mask_box else "setBorderImage" %}
 {{ declare_initial_function(property_id) }}
 {
     NinePieceImage image(state.style()->{{getter}}());
     {%- if modifier_type == "Outset" %}
-    image.setOutset(BorderImageLengthBox({{ (["Length(0, Fixed)"]*4) | join(", ") }}));
+    image.setOutset(Length(0, Fixed));
     {%- elif modifier_type == "Repeat" %}
     image.setHorizontalRule(StretchImageRule);
     image.setVerticalRule(StretchImageRule);
     {%- elif modifier_type == "Slice" and is_mask_box %}
     // Masks have a different initial value for slices. Preserve the value of 0 for backwards compatibility.
     image.setImageSlices(LengthBox({{ (["Length(0, Fixed)"]*4) | join(", ") }}));
     image.setFill(true);
     {%- elif modifier_type == "Slice" and not is_mask_box %}
     image.setImageSlices(LengthBox({{ (["Length(100, Percent)"]*4) | join(", ") }}));
     image.setFill(false);
     {%- elif modifier_type == "Width" %}
-    // Masks have a different initial value for widths. Preserve the value of 0 for backwards compatibility.
-    image.setBorderSlices(BorderImageLengthBox({{ (["1.0"]*4) | join(", ") if not is_mask_box }}));
+    // Masks have a different initial value for widths. Preserve the value of 'auto' for backwards compatibility.
+    image.setBorderSlices({{ "Length(Auto)" if is_mask_box else "1.0" }});
     {%- endif %}
     state.style()->{{setter}}(image);
 }
 
 {{ declare_inherit_function(property_id) }}
 {
     NinePieceImage image(state.style()->{{getter}}());
     {%- if modifier_type == "Outset" %}
     image.copyOutsetFrom(state.parentStyle()->{{getter}}());
     {%- elif modifier_type == "Repeat" %}
@@ skipping 307 matching lines @@
     } else if (value->isImageValue()) {
         {{ set_value(property) }}(ShapeValue::createImageValue(state.styleImage({{property_id}}, value)));
     }
 }
 {%- endmacro %}
 
 {{ apply_value_shape("CSSPropertyShapeInside") }}
 {{ apply_value_shape("CSSPropertyShapeOutside") }}
 
 } // namespace WebCore