nl_tokens: draw a line at when from y as far as len pixels with attrs .
pl_tokens: function ( when , len , attrs ) { var x = time_x ( when ) ; var end_y = ui . y + len ; var e = paper . <mask> ( "M" + x + "," + ui . y + " " + "L" + x + "," + end_y ) . attr ( attrs || { } ) ; return e ; }