SkSL: implement full support for separate textures and samplers.

This extends the support for separate textures and samplers to include 1D, 2D,
3D, ExternalOES, Cube, 2DRect, Buffer and ISampler2D. The new texture types are
now mandatory for a texturesampler which generates SPIR-V, so we can remove the
special case code for 2D previously landed.

Change-Id: Iec4bd6dc456169e6f4914ac416a10cd9720c42e0
Reviewed-by: Ethan Nicholas <>
Commit-Queue: Stephen White <>
3 files changed