RFR: 8151431: DateFormatSymbols triggers this.clone() in the constructor

[Masayoshi Okutsu]

Hi all,

Please review the fix for JDK-8151431. clone() is no longer called to 
create a cache entry.

Issue:
https://bugs.openjdk.java.net/browse/JDK-8151431
Webrev:
http://cr.openjdk.java.net/~okutsu/9/8151431/webrev.00/

Thanks,
Masayoshi