JDK 14 RFR JDK-8231913: add section on "conditionally serializable" collections

[Stuart Marks]

Hi,

Per discussion earlier in this thread, Joe had filed

     https://bugs.openjdk.java.net/browse/JDK-8231913

as an RFE to add this text to the Collection interface spec. Please review the 
corresponding CSR, which contains the updated, proposed specification text:

     https://bugs.openjdk.java.net/browse/JDK-8231977

(To indicate review/approval of a CSR, please edit the CSR issue and add your 
OpenJDK name to the "Reviewed By" box.)

Thanks,

s'marks