RFR [15] 8244342: Compilation warnings about unexpected serialization related method signatures.

Hi, Please review a fix for the compilation warnings. Thanks Roger for the detailed instructions! If you could verify the fix with the work-in-progress processor, that would be great too. Regular build and test passed. https://bugs.openjdk.java.net/browse/JDK-8244342 http://cr.openjdk.java.net/~joehw/jdk15/8244342/webrev/ Thanks, Joe