[9] Review request for 8164032 JViewport backing store image is not scaled on HiDPI display

[Alexandr Scherbatiy]

Hello,
Could you review the fix:
  bug: https://bugs.openjdk.java.net/browse/JDK-8164032
  webrev: http://cr.openjdk.java.net/~alexsch/8164032/webrev.00

  The fix scales the JViewport backing store image when graphics 
transform is not identity.

 Thanks,
 Alexandr.