Do clean up in PlatformFontMac

Do not try to derive one weight of font from another.
Use the API to directly generate them.

PlatformFontMacTest.FontWeightAPIConsistency tested that
our understanding of shifting weights up and down was
correct. The code no longer shifts weights up and down
as that is unreliable and version-specific, so there is
no need to test weight shifting and it is removed.

This also fixes Big Sur issues.

This re-lands c2e39ede4e8a9a7a1f944af41475dae7cb079b26.
It turns out that DCHECKs do evaluate everything in them
so wrap it with DCHECK_IS_ON().

Bug: 1101426
Change-Id: I1194b4aa127223456b432d12c47d248264d87c85
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2342387
Reviewed-by: Elly Fong-Jones <[email protected]>
Commit-Queue: Avi Drissman <[email protected]>
Cr-Commit-Position: refs/heads/master@{#796478}
5 files changed