Reland "Reland "uniform Ptr (UPtr) is a sub class of Ptr""

This is a reland of ea17e2499d66048e73f5b1bc9ca64bec79e9a844

Original change's description:
> Reland "uniform Ptr (UPtr) is a sub class of Ptr"
>
> This is a reland of cef047a4904e8c8b4e3f8888c4fa19705eeec166
>
> Fix strides in SkVMTest to be the right size.
>
> Original change's description:
> > uniform Ptr (UPtr) is a sub class of Ptr
> >
> > A pointer for a Uniform (UPtr) is a sub type of a Ptr. Everywhere you
> > can use a Ptr a UPtr will work, but you can't use Ptr where you need
> > a UPtr. All the UPtr instructions uniformF, gather32, etc are expected
> > to be hoisted and therefore loaded only once. While the varyings
> > instructions like load32, etc. are expected to remain in the body
> > of the loop, and be evaluated each time through the loop.
> >
> > Change-Id: I4fe6458c2a4614872ed67cda1e81b05ea8a9e69e
> > Reviewed-on: https://skia-review.googlesource.com/c/skia/+/436297
> > Commit-Queue: Herb Derby <herb@google.com>
> > Reviewed-by: Brian Osman <brianosman@google.com>
>
> Change-Id: I858fa1224452ec801b6186fede353849edc895b5
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/436564
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Herb Derby <herb@google.com>

Change-Id: I774e710724c99a41d0d160e88a2b723f66e03861
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/436821
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
7 files changed