def write_json_base64(str)
      @context.write(trans)
      trans.write(@@kJSONStringDelimiter)
      trans.write(Base64.strict_encode64(str))
      trans.write(@@kJSONStringDelimiter)
    end
def write_json_base64(str)
      @context.write(trans)
      trans.write(@@kJSONStringDelimiter)
      trans.write(Base64.strict_encode64(str))
      trans.write(@@kJSONStringDelimiter)
    end
Write out the contents of the string as JSON string, base64-encoding
 the string's contents, and escaping as appropriate