Since commit c7c5cf9b ClutterCloneTexture causes an extra paint of the
source actor during the paint run of the cloned texture if the source
is not yet visible. When the stage is first shown it is redrawn
immediatly before it is mapped which means get_paint_visibility will
fail on the source actor so the inner paint will be run. The paint
guards were a global variable so they didn't cope with a second actor
being painted.
The breakage didn't occur until commit d510a4b0 because
get_paint_visibility was also broken.
c68cf3564e