Update the Linux watcher to accommodate changes in [Directory.watch].

This also removes the extra time allotted for the test since issue
14606 is now mitigated.

R=rnystrom@google.com
BUG=15446

Review URL: https://codereview.chromium.org//99483006

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/watcher@30874 260f80e4-7a28-3924-810f-c04153c831b5