Remove SkIsS16 and SkIsU16.

SkIsS16 can be replaced with SkTFitsIn<int16_t> and SkIsU16 is never
used.

Change-Id: I734f677149fab102cdb295a7b34faa3e3089134a
Reviewed-on: https://skia-review.googlesource.com/38600
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
2 files changed