Reland "Remove double support from SkSL."

This reverts commit 59aa4b7187c6a6a6c9ee43dfd70224d5957bc55a.

Reason for revert: ASAN failures were actually unrelated to this CL.

Original change's description:
> Revert "Remove double support from SkSL."
> 
> This reverts commit 71a35d49b73448e646c82538ecb009fc68471580.
> 
> Reason for revert: ASAN failures on swarming bots
> 
> Original change's description:
> > Remove double support from SkSL.
> > 
> > Doubles are not supported by Metal or GLSL pre-4.0, are not supported in
> > most backends, and aren't used in any GMs. There isn't any good way to
> > use them in new code as it would just degrade to float on many of our
> > supported platforms. (This is assuming that our backends actually know
> > how to degrade doubles to floats, which is not universally the case.)
> > 
> > Change-Id: Ieacc69db4bdacca104a15a6eef33e05f977d1ffa
> > Bug: skia:10299
> > Reviewed-on: https://skia-review.googlesource.com/c/skia/+/292846
> > Commit-Queue: John Stiles <johnstiles@google.com>
> > Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
> > Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
> > Auto-Submit: John Stiles <johnstiles@google.com>
> 
> TBR=bsalomon@google.com,ethannicholas@google.com,johnstiles@google.com
> 
> Change-Id: I175e42420bcae8dfacd0bfeb269dd84e0b3c9d25
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: skia:10299
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293268
> Reviewed-by: John Stiles <johnstiles@google.com>
> Commit-Queue: John Stiles <johnstiles@google.com>

TBR=bsalomon@google.com,ethannicholas@google.com,johnstiles@google.com

# Not skipping CQ checks because this is a reland.

Bug: skia:10299
Change-Id: I5cdd71a1512228175514a0d29e19ae91afc78b6a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293273
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
10 files changed