question: gets the mode for the x-frame-options header value . for example , deny , sameorigin , allow-from . can not be null . concode_field_sep String XFRAME_OPTIONS_HEADER concode_elem_sep String mode concode_elem_sep XFrameOptionsMode frameOptionsMode concode_elem_sep AllowFromStrategy allowFromStrategy concode_field_sep void writeHeaders
target: String function ( ) { return mode ; }