Bug 1493 - GL ES does not work since Jan 9 in PowerVR SGX 535, Intel
The mapped flag needs to be set on the stage otherwise
clutter_actor_queue_redraw will never queue a redraw and never draw
anything.
In these two backends there is not really a way to hide the stage so
they both set the mapped flag immediatly when clutter_actor_show is
called.
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