I haven't tested this elsewhere yet, but I've encountered these issues on OSX:
(1) As per the title, content is not redrawn until window maximization or fullscreen transition is completed. And I have not checked yet but I suspect JS execution is also suspended.
(2) Enlarging the window also exhibits a redraw delay; it's most apparent when you drag the left or top edges of the window ...
Another small matter is the fact that there is no way to set the background color of the backing window, and the window is shown before the (in this case) minimal 'boot' html -- which is a little jarring.
All that said, thanks -- this is a useful gizmo. :)