Generate enum/getters/setters/mappings for box-sizing.

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 858 matching lines @@
       field_template: "external",
       field_type_path: "platform/Length",
       field_group: "surround",
       default_value: "Length()",
     },
     {
       name: "box-shadow",
       converter: "ConvertShadowList",
       interpolable: true,
     },
-    "box-sizing",
+    {
+      name: "box-sizing",
+      field_template: "keyword",
+      type_name: "EBoxSizing",
+      default_value: "content-box",
+      keywords: ["content-box", "border-box"],
+      field_group: "box",
+    },
     {
       name: "break-after",
       // Storage for this property also covers these legacy properties:
       // page-break-after, -webkit-column-break-after
       default_value: "auto",
       field_template: "keyword",
       keywords: [
         "auto", "avoid", "avoid-column", "avoid-page", "column", "left", "page", "recto", "right", "verso"
       ],
       type_name: "EBreakBetween",
@@ skipping 2418 matching lines @@
     {
       name: "-webkit-transition-timing-function",
       alias_for: "transition-timing-function",
     },
     {
       name: "-webkit-user-select",
       alias_for: "user-select",
     },
   ],
 }