Code Review Request For JDK-8091170: Compile-time warnings in prism-es2 code

[Chien Yang]

Hi Kevin,

Please review the proposed fix which was moved from JDK-8090866 as per 
our conversation:

JIRA: https://bugs.openjdk.java.net/browse/JDK-8091170
Webrev: http://cr.openjdk.java.net/~ckyang/JDK-8091170/webrev.00/

Thanks,
- Chien