Tests must call Render before ExtensionManager
This issue was created automatically from an original Mantis Issue. Further discussion may take place here.
The tests Charts-TestMultipleScalarsToColors, TestMultiTexturing, and TestMultiTexturingTransform should call Render on the render window before checking for OpenGL extensions.
In OSMesa calling glGetString without a current context causes a segfault.
The documentation for vtkOpenGLExtensionManager clearly says that just creating the render window does not create a context and make it current.