RFR: 8050091: LinkedList has incorrect implementation comment

[Martin Buchholz]

On Sat, Jun 27, 2015 at 5:46 AM, Ivan Gerasimov <ivan.gerasimov at oracle.com>
wrote:

> Hi Martin!
>
> Thank you for this cleanup!
> Removal of wrong comments looks fine.
>
> But your webrev contains commented checkInvariants() method.
> Is it a leftover from debugging or something?
>

It could be used for debugging, but it's primarily the (corrected!)
documentation of the invariants of the fields, expressed in executable code.