[9] Code Review Request JDK-8154509: Remove the word impl_ in the name of private methods and members

[Chien Yang]

Hi Kevin,

Please review this simple name change cleanup fix.

JIRA: https://bugs.openjdk.java.net/browse/JDK-8154509
Webrev: http://cr.openjdk.java.net/~ckyang/JDK-8154509/webrev.00/

Thanks,
- Chien