Generate subgroup StyleSurroundData in ComputedStyle.

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 43 matching lines @@
     // in the .h file for this property, and also used in CSSPropertyAPIFiles.h.tmpl to
     // generate declarations for only the methods this property has implementations for.
     api_methods: {
       default: [],
       valid_type: "list",
        // This list must be an ordered, complete list of methods whose names match those
        // defined in CSSPropertyDescriptor.h.
       valid_values: ["parseSingleValue", "parseShorthand"],
     },
 
+    // - field_group
+    // Name of the group that this field belongs to. Fields in the same group are stored
+    // together as a nested class inside ComputedStyle and dynamically allocated on use.
+    // Leave this out if the field is stored directly on ComputedStyle.
+    field_group: {
+      value_type: "str"
+    },
+
     // - field_template
     // Affects how the interface to this field is generated.
     // TODO(sashab, meade): Remove this once TypedOM types are specified for
     // every property, since this value can be inferred from that.
     field_template: {
       valid_values: [
         // Field is stored as an enum and has a initial/getter/setter/resetter.
         "keyword",
         // Field stores a primitive value like int/bool. The type is specified by
         // type_name. The interface has a initial/getter/setter/resetter.
@@ skipping 715 matching lines @@
     },
     {
       name: "bottom",
       api_class: "CSSPropertyAPIMargin",
       api_methods: ["parseSingleValue"],
       converter: "ConvertLengthOrAuto",
       interpolable: true,
       keywords: ["auto"],
       supports_percentage: true,
       typedom_types: ["Length"],
+      field_template: "external",
+      field_type_path: "platform/Length",
+      field_group: "surround",
+      default_value: "Length()",
     },
     {
       name: "box-shadow",
       converter: "ConvertShadowList",
       interpolable: true,
     },
     "box-sizing",
     {
       name: "break-after",
       // Storage for this property also covers these legacy properties:
@@ skipping 382 matching lines @@
     },
     {
       name: "left",
       api_class: "CSSPropertyAPIMargin",
       api_methods: ["parseSingleValue"],
       converter: "ConvertLengthOrAuto",
       interpolable: true,
       keywords: ["auto"],
       supports_percentage: true,
       typedom_types: ["Length"],
+      field_template: "external",
+      field_type_path: "platform/Length",
+      field_group: "surround",
+      default_value: "Length()",
     },
     {
       name: "letter-spacing",
       api_class: "CSSPropertyAPILetterAndWordSpacing",
       api_methods: ["parseSingleValue"],
       converter: "ConvertSpacing",
       inherited: true,
       initial: "InitialLetterWordSpacing",
       interpolable: true,
     },
@@ skipping 379 matching lines @@
     },
     {
       name: "right",
       api_class: "CSSPropertyAPIMargin",
       api_methods: ["parseSingleValue"],
       converter: "ConvertLengthOrAuto",
       interpolable: true,
       keywords: ["auto"],
       supports_percentage: true,
       typedom_types: ["Length"],
+      field_template: "external",
+      field_type_path: "platform/Length",
+      field_group: "surround",
+      default_value: "Length()",
     },
     {
       name: "r",
       api_class: "CSSPropertyAPIStrokeOrLength",
       converter: "ConvertLength",
       interpolable: true,
       svg: true,
     },
     {
       name: "rx",
@@ skipping 298 matching lines @@
     },
     {
       name: "top",
       api_class: "CSSPropertyAPIMargin",
       api_methods: ["parseSingleValue"],
       converter: "ConvertLengthOrAuto",
       interpolable: true,
       keywords: ["auto"],
       supports_percentage: true,
       typedom_types: ["Length"],
+      field_template: "external",
+      field_type_path: "platform/Length",
+      field_group: "surround",
+      default_value: "Length()",
     },
     {
       name: "touch-action",
       api_class: true,
       api_methods: ["parseSingleValue"],
       converter: "ConvertFlags<TouchAction>",
       type_name: "TouchAction",
     },
     {
       name: "transform",
@@ skipping 1263 matching lines @@
     {
       name: "-webkit-transition-timing-function",
       alias_for: "transition-timing-function",
     },
     {
       name: "-webkit-user-select",
       alias_for: "user-select",
     },
   ],
 }