Make gm tool able to read and write image files in the same run
Make gm tool able to read and write image files in the same run

BUG=http://code.google.com/p/skia/issues/detail?id=571
Review URL: https://codereview.appspot.com/6052050

csulmone/skia,csulmone/skia,csulmone/skia,csulmone/skia