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/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index 03a2db0..f50311b 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -217,7 +217,7 @@
 
     if (!desc.fColorSpace) {
         // This happens if we were constructed from SkColors, so our colors are really sRGB
-        fColorSpace = SkColorSpace::MakeNamed(SkColorSpace::kSRGBLinear_Named);
+        fColorSpace = SkColorSpace::MakeSRGBLinear();
     } else {
         // The color space refers to the float colors, so it must be linear gamma
         SkASSERT(desc.fColorSpace->gammaIsLinear());
@@ -740,12 +740,12 @@
                 case GradientBitmapType::kSRGB:
                     info = SkImageInfo::Make(kCache32Count, 1, kRGBA_8888_SkColorType,
                                              kPremul_SkAlphaType,
-                                             SkColorSpace::MakeNamed(SkColorSpace::kSRGB_Named));
+                                             SkColorSpace::MakeSRGB());
                     break;
                 case GradientBitmapType::kHalfFloat:
                     info = SkImageInfo::Make(
                         kCache32Count, 1, kRGBA_F16_SkColorType, kPremul_SkAlphaType,
-                        SkColorSpace::MakeNamed(SkColorSpace::kSRGBLinear_Named));
+                        SkColorSpace::MakeSRGBLinear());
                     break;
                 default:
                     SkFAIL("Unexpected bitmap type");