message: support required member
diff: @@ -200,6 +200,7 @@ function convertDictionaryMember(member: webidl2.DictionaryMemberType): Browser.
  return {
  name: member.name,
  default: member.default ? convertConstantValue(member.default) : undefined,
  + "required": member.required ? 1 : undefined,
  ...convertIdlType(member.idlType)
  }
  }
  