Bind ClearFlags, this should probably be implicit
[Pick] Add Mode fallback, used for both using Depth() as a fallback if shader doesn't have DepthNormal() and to move VrForward() to just Forward()
Just use DepthNormalPrepassLayer, use depthnormal mode again
[Pick] VrForward > Forward, reverse fallback so that old shaders with VrForward use that still