kbr said he will take a look since he has a mac that may reproduce this failure.

I get 

failed: completeness.renderable.renderbuffer.color0.rgb5_a1: Framebuffer checked as incomplete, expected complete
failed: completeness.renderable.texture.color0.rgb5_a1: Framebuffer checked as incomplete, expected complete
failed: completeness.renderable.texture.color0.rgba_unsigned_short_5_5_5_1: Framebuffer checked as incomplete, expected complete

Which makes sense since rgb5_a1 is not renderable there.

The plan was to make these non-renderable in the spec and update the tests, correct?

That was what we discussed. Now that this is only a bug in one GPU on Mac, I am not sure if other browsers will agree to this. I hope they do.

Opened https://github.com/KhronosGroup/WebGL/pull/1755 for that purpose. This could be discussed more in the F2F

Mac NVidia is not our target platform for WebGL2's initial release. Make it non-blockng.