remove SkColorSpace_Base

The type SkColorSpace_Base doesn't need to exist.  Its one type() query
can be answered instead by toXYZD50().

Now all that's left in the file is SkGammas, so rename it to SkGammas.h.

Change-Id: Id60ddbfb342accfd5674ae89b37a24a6583ef7b8
Reviewed-on: https://skia-review.googlesource.com/99702
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
41 files changed