Generate getters/setters for remaining flex-* properties.

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 6a38fe1dccbab2403d975d615e28c32646eacd50..391d98a68ddaba5f07bc55e3b8e3c5b5e7538f3e 100644
--- a/third_party/WebKit/Source/core/css/CSSProperties.json5
+++ b/third_party/WebKit/Source/core/css/CSSProperties.json5
@@ -1208,7 +1208,7 @@
       converter: "ConvertLengthOrAuto",
       interpolable: true,
       type_name: "Length",
-      field_template: "storage_only",
+      field_template: "external",
       default_value: "Length(kAuto)",
       field_group: "rare-non-inherited->flexible-box",
     },
@@ -1226,7 +1226,7 @@
       api_methods: ["parseSingleValue"],
       interpolable: true,
       type_name: "float",
-      field_template: "storage_only",
+      field_template: "primitive",
       default_value: "0.0f",
       field_group: "rare-non-inherited->flexible-box",
     },
@@ -1236,7 +1236,7 @@
       api_methods: ["parseSingleValue"],
       interpolable: true,
       type_name: "float",
-      field_template: "storage_only",
+      field_template: "primitive",
       default_value: "1.0f",
       field_group: "rare-non-inherited->flexible-box",
     },