Fix a typo in path_set_test. I'd have sworn I fixed this in the orignal CL. R=rnystrom@google.com TBR Review URL: https://codereview.chromium.org//67973003 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/watcher@30173 260f80e4-7a28-3924-810f-c04153c831b5