Transparent regions are black on GLES target.

[Thomas Schüßler <vindolin gmail com>]

I have a problem with ClutterCanvas transparency on our GLES target 
(Mali 400 GPU).
All transparent regions turn out black when drawing to the cairo context.

On my Ubuntu box everything works as expected.

Setting the content from a GdkPixbuf with alpha channel works perfectly 
though.

This is the test that fails on the GLES machine:
https://gist.github.com/vindolin/96b247d624e94b269b8c

This here runs perfectly:
https://github.com/vindolin/Clutter-Python-examples/blob/master/ninepatch_actor.py

Thanks,
Thomas