Re: Standardizes use of empty extents in pure heights and skylines. (issue 7310075)

[k-ohara5a5a]

https://codereview.appspot.com/7310075/diff/67001/lily/skyline.cc
File lily/skyline.cc (right):

https://codereview.appspot.com/7310075/diff/67001/lily/skyline.cc#newcode370
lily/skyline.cc:370: if (x1 >= last_end)
Oops.  This controls whether to put an empty, -inf height, building in
the gap. (When do we ever want Building data structures marking gaps?
The skyline concept seems to allow for gaps.)

These zero-width anti-buildings would not have any effect, except that
they are drawn (issue 3311) but they are not the boxes that surprised us
when they disappeared (issue 3161).

Probably safest to put back the x1 > last_end + EPS

https://codereview.appspot.com/7310075/