chromium/third_party/blink/renderer/core/preferences/preference_values.json5

{
  metadata: {
    namespace: "preference_values",
    export: "CORE_EXPORT",
  },

  data: [
    "custom",
    "dark",
    "less",
    "light",
    "more",
    "no-preference",
    "reduce",
  ],
}