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/ImageTest.cpp b/tests/ImageTest.cpp
index 67ddd6c..c4f8abb 100644
--- a/tests/ImageTest.cpp
+++ b/tests/ImageTest.cpp
@@ -131,7 +131,7 @@
     canvas->clear(SK_ColorCYAN);
     return SkImage::MakeFromPicture(recorder.finishRecordingAsPicture(), SkISize::Make(10, 10),
                                     nullptr, nullptr, SkImage::BitDepth::kU8,
-                                    SkColorSpace::MakeNamed(SkColorSpace::kSRGB_Named));
+                                    SkColorSpace::MakeSRGB());
 };
 #endif
 // Want to ensure that our Release is called when the owning image is destroyed
@@ -486,7 +486,7 @@
 
     sk_sp<SkColorSpace> dstColorSpaces[] ={
         nullptr,
-        SkColorSpace::MakeNamed(SkColorSpace::kSRGB_Named),
+        SkColorSpace::MakeSRGB(),
     };
 
     for (auto& dstColorSpace : dstColorSpaces) {