Code Review Request: 7168172: (fs) Files.isReadable slow on Windows

[Kurchi Hazra]

Hi,

    Files.isReadable() is slow on Windows, since it involves reading the 
DACL and computing the effective access to the file. [1]
However, it is faster to simply open the file being checked and close 
it. In the case of a directory then, a DirectoryStream can
be opened and closed to check the same.

Bug: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7168172
Webrev: http://cr.openjdk.java.net/~khazra/7168172/webrev.00/

Thanks to Alan for helping out a lot with this fix.

- Kurchi

[1] http://mail.openjdk.java.net/pipermail/nio-dev/2012-May/001667.html