[9] Review request: 8166382 [hidpi] Ubuntu 16.04: invalid coordinates when using glass robot

[Jim Graham]

JBS: https://bugs.openjdk.java.net/browse/JDK-8166382
webrev: http://cr.openjdk.java.net/~flar/JDK-8166382/webrev.00/

Pretty self-explanatory fix...

                        ...jim