In bug 1186061 I'm going to disable compositor-thread (off-main-thread, OMT) animation of transform animations that have backface-visibility:hidden. This bugs covers reenabling them, which I believe means detecting that the transform animation has crossed from showing the front face to showing the back face, and thus that we need to rerender. This gets complicated in combination with preserve-3d (which we also don't support doing on the compositor).

I don't think we need to rerender when we transition, since any 'backface' that is expected to become visible should be a separate element (with a separate layer). I think we can get away with just having a flag specifying that the backface is hidden, and have the compositor cull the layer if necessary.

According the discussion on a mail loop with dbaron and Matt, we are ready to move backface hidden and transform animation to the compositor.

Cool! So what's necessary here? Just a layer flag for backface-visibility, and the LayerManagerComposite code to not render those layers if they face away from the camera?

Does this not work already? http://searchfox.org/mozilla-central/source/gfx/layers/composite/ContainerLayerComposite.cpp#202

Oh! And the patch in bug 779598 already removes the backface-visibility check.

The problem that this bug tried to fix had been fixed by other bugs.

Reopening since I am going to fix only preserve-3d case in bug 779598.