RFR (T): 8224042 Add private alignDown method to MappedByteBuffer

[Alan Bateman]

On 16/05/2019 15:49, Andrew Dinn wrote:
> Please review this trivial change to MapperByteBuffer which encapsulates
> the page align down operation in a suitably named method.
>
> JIRA:   https://bugs.openjdk.java.net/browse/JDK-8224042
> webrev: http://cr.openjdk.java.net/~adinn/8224042/webrev.00/
>
Looks okay (private static, as Thomas prefers, is fine too).

-Alan