[12] RFR: 8217892: Clarify the support for the new Japanese era in java.time.chrono.JapaneseEra

[Chris Hegarty]

Naoto,

> On 31 Jan 2019, at 00:51, naoto.sato at oracle.com wrote:
> 
> ..
> https://bugs.openjdk.java.net/browse/JDK-8217939
> http://cr.openjdk.java.net/~naoto/8217892/webrev.00/

The changes look good. Reviewed.

-Chris.