Reason for revert:
Co-centered sample locations are not needed to do stencil clip with mixed samples
Original issue's description:
> Implement stencil clipping in mixed sampled render targets
>
> This change enables multisampled clipping for mixed sampled
> render targets. Previously clipping in mixed samples config
> behaved the same as in the gpu config.
>
> In order to retrofit non-MSAA draw methods, programmable sample
> locations are used in order to colocate all samples at (0.5, 0.5).
> Requires support for NV_sample_locations.
>
> BUG=skia:4399
>
> Committed:
> https://skia.googlesource.com/skia/+/3e77ba96d56d15db30ac6d8ccb900e30aafcbb16
BUG=skia:
Review URL: https://codereview.chromium.org/1415873011
7e806f3f8a