Generate getters/setters for border-image.

third_party/WebKit/Source/core/css/CSSProperties.json5

 {
 // This file specifies all the CSS properties we support and the necessary
 // information for our code generation. The various supported arguments
 // are described below with example usage
 
   parameters: {
     // - alias_for: "other-property"
     // Properties specifying alias_for should be virtually identical to the
     // properties they alias. Minor parsing differences are allowed as long as
     // the CSSValues created are of the same format of the aliased property.
@@ skipping 2166 matching lines @@
       name_for_methods: "HorizontalBorderSpacing",
       field_template: "primitive",
       type_name: "short",
       field_group: "inherited",
       default_value: "0",
     },
     {
       name: "-webkit-border-image",
       api_class: true,
       custom_value: true,
-      initial: "InitialNinePieceImage",
     },
     {
       name: "-webkit-border-vertical-spacing",
       api_class: "CSSPropertyAPIWebkitBorderSpacing",
       api_methods: ["parseSingleValue"],
       converter: "ConvertComputedLength<short>",
       inherited: true,
       interpolable: true,
       name_for_methods: "VerticalBorderSpacing",
       field_template: "primitive",
@@ skipping 1145 matching lines @@
     {
       name: "-webkit-transition-timing-function",
       alias_for: "transition-timing-function",
     },
     {
       name: "-webkit-user-select",
       alias_for: "user-select",
     },
   ],
 }