Reduce scaling of large SDF glyphs on Mac.

It appears that the Mac glyph rasterizer doesn't work well with our
AA-based SDF generator -- the SDFs produced have more aliasing than
expected. This CL changes the Mac to use 256 as its highest SDF size,
and only scale down from there.

More work may need to be done -- the best solution may be to generate
the SDFs directly from the path rather than the rasterized glyph.

Bug: 1003270
Change-Id: I7f11620a5628b6c1095b02d588d5026bf5a924e8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/254636
Reviewed-by: Herb Derby <herb@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
2 files changed