bug 908232 - step 1 - Refactor the WebGL state tracking - r=jgilbert
bug 908232 - step 2 - [WebGL 2.0] Add RASTERIZER_DISCARD tracking - r=jgilbert
bug 907946 - re-enable EXT_packed_depth_stencil on OS X 10.9 - r=bjacob,jgilbert