pixman-renderer, gl-renderer: Destroy surface state with the renderer

Previously the renderers destroy function assumed they are only called
when the compositor is shutting down and that the compositor had
already destroyed all the surfaces. However, if a runtime renderer
switch would be done, the surface state would be leaked.

This patch adds a destroy_signal to the pixman and gl renderers. The
surface state objects will listen for that signal and destroy
themselves if needed.

This is a step towards runtime switchable renderers.
2 files changed