Work around more browser bugs
Work around more browser bugs

drawImage is buggy in Firefox and Chrome. Talking with
Ian Hixie showed that these are in fact browser bugs.

https://code.google.com/p/chromium/issues/detail?id=176714
https://bugzilla.mozilla.org/show_bug.cgi?id=842110

There are still some redraw issues, but I think these are of my
own fault, not browser bugs. You never know, though.

magcius/xplain,magcius/xplain