While refactoring Glass to work with MTL,ES2 & SW pipeline under https://bugs.openjdk.org/browse/JDK-8325379, 2 issues were noticed which can be updated in follow-up bug.

1) Remove references to CGLContextObj from GLassLayer3D
2) Check whether we need to set CAOpenGLLayer's opaque flag to the value of the NSWindow's opaque flag in GlassWindow.m. This flag was added under https://bugs.openjdk.org/browse/JDK-8095004 to fix issues in PickTest3D but in current code PickTest3D works properly without this code.