Fix non-blitting behavior

/cc @tonysyu

what os/backend?  

There was an issue with this in mpl recently:  https://github.com/matplotlib/matplotlib/pull/2844 however, thinking about it again, it looks like I was confused by what layer of `draw` this is calling (the mpl layer or the toolkit layer).  It looks like `draw_idle` should, be default, just call draw: https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/backend_bases.py#L1985

Sorry for the drive-by comments, what do you mean by didn't work?