<AWT Dev> [9] Review request for 8044157: improve recently submitted AWT_Mixing tests

[Yuri Nesterenko]

Hi,

please review this change for RFE
https://bugs.openjdk.java.net/browse/JDK-8044157

Webrev is in
http://cr.openjdk.java.net/~yan/8044157/webrev.00

Thanks,
-yan
_______________
In this change, we remove an exact copy of one helper class
and change some stray System.exits to RuntimeExceptions.

Tested on 2 different Linux systems, on OS X and
2 Windows (7, 8.1).