When we reset or recreate the d3d9 device we tell the main thread to invalidate and repaint everything. This is probably not necessary. We would get better performance and cleaner code if we just re-upload all our textures and re-composite instead. See https://bugzilla.mozilla.org/show_bug.cgi?id=900248#c43 for details. If we do this we can remove the InvalidateAll IPC message and the compositor would no longer need to hold a reference to its CompositorParent.