clutter/frame-clock: Handle reschedule then dispatch results in idle

A frame clock dispatch doesn't necessarily result in a frame drawn,
meaning we'll end up in the idle state. However, it may be the case that
something still requires another frame, and will in that case have
requested one to be scheduled. In order to not dead lock, try to
reschedule directly if requested after dispatching, if we ended up in
the idle state.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1285

clutter/clutter/clutter-frame-clock.c

@@ -419,6 +419,7 @@ clutter_frame_clock_dispatch (ClutterFrameClock *frame_clock,
           break;
         case CLUTTER_FRAME_RESULT_IDLE:
           frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_IDLE;
+          maybe_reschedule_update (frame_clock);
           break;
         }
       break;