Fixes a regression introduced in
bd26d79b17
The issue was observed in the DemoRunner when enabling the OpenGL
renderer and then switching to the LookAndFeel V1.
The cause of the problem was the creation of a secondary OpenGL-backed
Graphics instance in the DropShadowEffect. This temporary context could
modify the OpenGL context state without restoring the state
appropriately on destruction. As a result, when the outer long-lived
OpenGL context resumed drawing, properties such as the viewport, bound
shader, shader uniform values, and bound framebuffer could all be
incorrect.
fb4159c436