@rtpg - the draw loop was continuing to run, but it would not display
For some reason the canvas would no longer update. I was unable to
determine when the problem occurred but did figure out how to get the
canvas to start displaying the images again. It was required that I resize
the canvas (I change the width by one pixel) and then redraw (it's
embarrassingly hackish). I current have it set to run every 30 seconds
through setTimeout, but will probably change to window.onfocus once I can
verify that gets called when coming out of sleep mode.