This code:

import matplotlib
matplotlib.use('agg')
from pylab import *
plot([1,2,5])
savefig("test")

causes Figure.draw to be called 155 times with the code currently in master.
With matplotlib 1.4.3, Figure.draw is called twice (once to create the PNG, and once to redraw the figure).
I am guessing that this has to do with the default implementation of draw_idle in FigureCanvasBase. Currently it calls draw().
So then if I change a property of the figure, the figure gets marked as stale, draw_idle is called, draw_idle calls draw, which resets the figure as non-stale.