Generate subgroup StyleSurroundData in ComputedStyle.

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

Index: third_party/WebKit/Source/core/css/CSSProperties.json5
diff --git a/third_party/WebKit/Source/core/css/CSSProperties.json5 b/third_party/WebKit/Source/core/css/CSSProperties.json5
index 5fadf17293a9b2457a45edca1cdd9816b8bbc7a2..13429fce23ca336aa1ac9e8c39a65328d2bb1c45 100644
--- a/third_party/WebKit/Source/core/css/CSSProperties.json5
+++ b/third_party/WebKit/Source/core/css/CSSProperties.json5
@@ -61,6 +61,14 @@
       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
@@ -804,6 +812,10 @@
       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",
@@ -1205,6 +1217,10 @@
       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",
@@ -1604,6 +1620,10 @@
       keywords: ["auto"],
       supports_percentage: true,
       typedom_types: ["Length"],
+      field_template: "external",
+      field_type_path: "platform/Length",
+      field_group: "surround",
+      default_value: "Length()",
     },
     {
       name: "r",
@@ -1922,6 +1942,10 @@
       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",
@@ -2699,6 +2723,10 @@
     {
       name: "border",
       longhands: "border-top-color;border-top-style;border-top-width;border-right-color;border-right-style;border-right-width;border-bottom-color;border-bottom-style;border-bottom-width;border-left-color;border-left-style;border-left-width;border-image-source;border-image-slice;border-image-width;border-image-outset;border-image-repeat",
+      field_template: "storage_only",
+      field_type_path: "core/style/BorderData",
+      field_group: "surround",
+      default_value: "BorderData()"
     },
     {
       name: "border-bottom",
@@ -2801,6 +2829,10 @@
     {
       name: "margin",
       longhands: "margin-top;margin-right;margin-bottom;margin-left",
+      field_template: "storage_only",
+      field_type_path: "platform/LengthBox",
+      field_group: "surround",
+      default_value: "LengthBox(Fixed)",
     },
     {
       name: "marker",
@@ -2825,6 +2857,10 @@
     {
       name: "padding",
       longhands: "padding-top;padding-right;padding-bottom;padding-left",
+      field_template: "storage_only",
+      field_type_path: "platform/LengthBox",
+      field_group: "surround",
+      default_value: "LengthBox(Fixed)",
     },
     {
       name: "page-break-after",