Fix memory leak in gm, suppress warnings from nvidia drivers

With these in place, GM will be down to one valgrind leak (http://code.google.com/p/skia/issues/detail?id=530) and one warning, both well-understood.

[TomH, 2012-03-15 13:09:54]

r3395 fixes the warning.

[epoger, 2012-03-15 13:35:26]

LGTM

[TomH, 2012-03-15 13:40:11]

Closed in r3396.