[Windows] HiDPI screenshot artifacts using glass Robot

JDK9 b128 + Windows 10 + HiDPI screen (scale > 100% was used).


Please compile/run the attached test code (TestSnapshot.java + BMPOutputStream.java) using
  -XaddExports:javafx.graphics/com.sun.glass.ui=ALL-UNNAMED
and compare the following images (all of them are attached):

- utils.png (screenshot taken via SwingFXUtils) - looks reasonable
- glassRobot.bmp (screenshot taken by means of glass robot) - NOK (see the artifacts); please note also that HiDPI flag here set to true
- AWTRobot.bmp (screenshot taken by means of AWT robot) - NOK (the same)

the image on the screen looks normally.

When running the same code for scale = 100%, no issues occur (at least the screenshots look reasonable)