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/tests/SkResourceCacheTest.cpp b/tests/SkResourceCacheTest.cpp
index 922acef..2141885 100644
--- a/tests/SkResourceCacheTest.cpp
+++ b/tests/SkResourceCacheTest.cpp
@@ -331,7 +331,7 @@
             return SkImage::MakeFromPicture(recorder.finishRecordingAsPicture(),
                                             SkISize::Make(10, 10), nullptr, nullptr,
                                             SkImage::BitDepth::kU8,
-                                            SkColorSpace::MakeNamed(SkColorSpace::kSRGB_Named));
+                                            SkColorSpace::MakeSRGB());
         });
     }
 }