nl_tokens: Inserts a BR element if the forced_root_block option is set to false or empty string
pl_tokens: function insertBr ( ) { var brElm , extraBr , marker ; if ( container && container . nodeType == 3 && offset >= container . nodeValue . length ) { // Insert extra BR element at the end block elements
   if ( ! tinymce . isIE && ! hasRightSideBr ( ) ) { brElm = dom . create ( 'br' ) ; rng . insertNode ( brElm ) ; rng . setStartAfter ( brElm ) ; rng . setEndAfter ( brElm ) ; extraBr = true ; } } brElm = dom . create ( 'br' ) ; rng . insertNode ( brElm ) ; // Rendering modes below IE8 doesn't display BR elements in PRE unless we have a \n before it
   if ( tinymce . isIE && parentBlockName == 'PRE' && ( ! documentMode || documentMode < 8 ) ) { brElm . parentNode . insertBefore ( dom . doc . createTextNode ( '\r' ) , brElm ) ; } // Insert temp marker and scroll to that
   marker = dom . create ( 'span' , { } , '&nbsp;' ) ; brElm . parentNode . insertBefore ( marker , brElm ) ; <mask> . scrollIntoView ( marker ) ; dom . remove ( marker ) ; if ( ! extraBr ) { rng . setStartAfter ( brElm ) ; rng . setEndAfter ( brElm ) ; } else { rng . setStartBefore ( brElm ) ; rng . setEndBefore ( brElm ) ; } selection . setRng ( rng ) ; undoManager . add ( ) ; }