RFR [14/java.xml] 8229388: ErrorHandler and ContentHandler contain ambiguous/unfinished specification

[Joe Wang]

Please review a specification claraficaiton/doc-only change to 
ErrorHandler and ContentHandler.

JBS: https://bugs.openjdk.java.net/browse/JDK-8229388
CSR: https://bugs.openjdk.java.net/browse/JDK-8229738
webrev: http://cr.openjdk.java.net/~joehw/jdk14/8229388/webrev/

Thanks,
Joe