There 5 open bugs which mention sun/java2d/OpenGL/XORPaint.java as a
test that fails in some cases and it is problem listed on the closed problem list.
But none of the bugs are specifically about this test.
Eg see https://bugs.openjdk.java.net/browse/JDK-8238720

A couple of the reasons it fails are
- sampling a pixel right on the boundary of a rectangle so that in some hidpi cases it is not the exact value expected
- painting only once and assuming it will not get repainted by bailing at the start of paint() on 2nd and later calls and so when it does, the screen grab is all white.

I'd like to stabilise it and move it to open so I need a new bug specific to this test.