Comment 10 for bug 531719

Though the question is begged:
Why hold a reference mThebesSurface to the surface if it will be recreated
each time it is used anyway?

The "we should fix this at some point" comment was removed here:
http://hg.mozilla.org/mozilla-central/rev/ef0221c2a188#l12.606

The fix with the smallest change looks like it is to just remove
mThebesSurface. (But ensuring child nsWindows are Destroy()ed might enable us to reuse mThebesSurface at some point.)