SkColorSpace: remove named API, add gamut API

BUG=skia:

Change-Id: I01c5e1874c9a034febc64e25b3aaafb5050393a6
Reviewed-on: https://skia-review.googlesource.com/8021
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Matt Sarett <msarett@google.com>
66 files changed