Sanitized the GTK nsDeviceContextSpecFactoryG, nsRenderingContextPS, nsDeviceContextPS, and nsDeviceContextSpecG by removing WIN32 dependencies. Added checks for null widgets in nsWidget and nsScrollbar GTK implementations. git-svn-id: svn://10.0.0.236/trunk@21472 18797224-902f-48f8-a5cc-f745e15eee43