[8u, 9] Review request for 8156094: ContextMenu shown at wrong position on Windows10 with Extended Screen

[Jim Graham]

bug: https://bugs.openjdk.java.net/browse/JDK-8156094

webrev for 9-dev: http://cr.openjdk.java.net/~flar/JDK-8156094/9-dev/webrev.00/
webrev for 8u-dev: http://cr.openjdk.java.net/~flar/JDK-8156094/8u-dev/webrev.00/

The two fixes ended up being closer than I thought due to an idiosyncrasy of how Windows arranges screens for system-dpi 
apps...

			...jim