Before this commit, opening collects/drracket/private/unit.rkt required
about 17.5 megabytes of memory and after this commit, it is down to
about 15 megabytes.
The precise measurement I did was to create a frame and a scheme:text%
object in it, record the result of current-memory-use, open the file,
and record current-memory-use again.
For comparison, using a text:standard-style-list% object instead of
the scheme:text% requires only about 4.1 megabytes. One difference
being that there are about 3x more snips (10,204 vs 33,901 (after the
commit)), since we have one snip for each region that has a different
color in the scheme:text version, and the text:standard-style-list has
no colors and thus about two per line (there are 5006 lines in the
file).
double clicking inside a string) and when clicking on close
parentheses (specifically, only special case close parens that are
actually parentheses according to the colorer, rather than special
casing all close parens).
