Sets font size automatically for a slide in presentations.
This method causes the font size to change as this frame is resized,
so that text height will be about 1/25 of slide height if this frame
is saved to an image.
Specified fractions indicate indicate how much of the slide is
available for this plot. These fractions may be less than one,
to leave room for titles, other plots, etc.
This method uses a default width/height aspect ratio = 4.0/3.0.
To explicitly specify the aspect ratio, use the method
#setFontSizeForSlide(double,double,double).