Covariant overrides on the Buffer Hierarchy redux

[Paul Sandoz]

Hi,

There was discussion here:

  http://mail.openjdk.java.net/pipermail/core-libs-dev/2014-April/026458.html

  https://bugs.openjdk.java.net/browse/JDK-4774077

  http://cr.openjdk.java.net/~rwarburton/buffer-overrides-1/

The patch looks good.

I have just one comment: can you check the tests to see if there are any redundant casts?

After that i will run a JPRT test and then will push for you.

Thanks,
Paul.