Created attachment 212715 [details] [review]
shaped-texture: never slice shape mask texture

Since Cogl doesn't support multi-texturing with sliced textures and the shape texture is combined with the texture-from-pixmap texture we need to make sure we never construct a sliced mask texture otherwise on some platforms without full npot texture support we can be left with blank white windows when Cogl detects the sliced texture and replaces the tfp texture with a default white texture.