RFR: 8154231: Simplify access to System properties from JDK code

[Claes Redestad]

Hello,

now that the sun.security.action package is encapsulated we can simplify 
internal code to get System properties.

Bug: https://bugs.openjdk.java.net/browse/JDK-8154231
Webrev: http://cr.openjdk.java.net/~redestad/8154231/webrev.01/

This adds a few convenience methods to GetPropertyAction[1] and 
GetIntegerAction[2]. Since the code calling into this can be 
streamlined, this leads to a net static footprint reduction of the 
java.base module and a tiny startup improvement.

Thanks!

/Claes

[1] 
http://cr.openjdk.java.net/~redestad/8154231/webrev.01/src/java.base/share/classes/sun/security/action/GetPropertyAction.java.udiff.html
[2] 
http://cr.openjdk.java.net/~redestad/8154231/webrev.01/src/java.base/share/classes/sun/security/action/GetIntegerAction.java.udiff.html