SkColorSpace: remove named API, add gamut API

Reland from: https://skia-review.googlesource.com/c/8021/

BUG=skia:

Change-Id: I18985f130587b15fccbc86b76b2bb5c49ba5ba8a
Reviewed-on: https://skia-review.googlesource.com/8136
Reviewed-by: Matt Sarett <msarett@google.com>
Commit-Queue: Matt Sarett <msarett@google.com>
diff --git a/bench/SkLinearBitmapPipelineBench.cpp b/bench/SkLinearBitmapPipelineBench.cpp
index 4e892b6..a0ed605 100644
--- a/bench/SkLinearBitmapPipelineBench.cpp
+++ b/bench/SkLinearBitmapPipelineBench.cpp
@@ -91,7 +91,7 @@
         sk_ignore_unused_variable(trash);
 
         fInfo = SkImageInfo::MakeN32Premul(width, height, fIsSRGB ?
-                                      SkColorSpace::MakeNamed(SkColorSpace::kSRGB_Named) : nullptr);
+                                      SkColorSpace::MakeSRGB() : nullptr);
     }
 
     bool isSuitableFor(Backend backend) override {