[9] Review request for 8174688: JavaFX Applet popup windows are in the wrong location

[Jim Graham]

JBS: https://bugs.openjdk.java.net/browse/JDK-8174688
webrev: http://cr.openjdk.java.net/~flar/JDK-8174688/webrev.00/

It was a one-ish-line-ish fix (just needed to invert one Y coordinate consistent with other cases, but it took a couple 
of lines to fetch the necessary data for inversion).

Still need to investigate if it fails on 8u-dev where we have nearly the same code and request a backport if necessary.

Will need to file a couple of follow-on bugs to investigate the way we flip Y coordinates to make sure there are no 
additional, but more subtle, bugs in there.  Until then, this one fix improves the popup window positioning for the 
9-dev release and makes the code more consistent with the way we handle the Mac inverted Y coordinate systems...

			...jim