nl_tokens: Returns the text needed for the current back button at anytime .
pl_tokens: function ( ) { var text = this . backButtonStack [ this . backButtonStack . length - 2 ] , useTitleForBackButtonText = this . getUseTitleForBackButtonText ( ) ; if ( ! useTitleForBackButtonText ) { if ( text ) { text = this . getDefaultBackButtonText ( ) ; } } return <mask> ; }