(Some) gradients are gamma and gamut correct on GPU

src/effects/gradients/SkLinearGradient.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Sk4fLinearGradient.h"
 #include "SkLinearGradient.h"
 #include "SkRefCnt.h"
@@ skipping 323 matching lines @@
     if (info) {
         commonAsAGradient(info);
         info->fPoint[0] = fStart;
         info->fPoint[1] = fEnd;
     }
     return kLinear_GradientType;
 }
 
 #if SK_SUPPORT_GPU
 
+#include "GrColorSpaceXform.h"
 #include "glsl/GrGLSLCaps.h"
 #include "glsl/GrGLSLFragmentShaderBuilder.h"
 #include "SkGr.h"
 
 /////////////////////////////////////////////////////////////////////
 
 class GrLinearGradient : public GrGradientEffect {
 public:
     class GLSLLinearProcessor;
 
@@ skipping 100 matching lines @@
     }
     if (args.fLocalMatrix) {
         SkMatrix inv;
         if (!args.fLocalMatrix->invert(&inv)) {
             return nullptr;
         }
         matrix.postConcat(inv);
     }
     matrix.postConcat(fPtsToUnit);
 
+    sk_sp<GrColorSpaceXform> colorSpaceXform = GrColorSpaceXform::Make(fColorSpace.get(),
+                                                                       args.fDstColorSpace);
     sk_sp<GrFragmentProcessor> inner(GrLinearGradient::Make(
-        GrGradientEffect::CreateArgs(args.fContext, this, &matrix, fTileMode)));
+        GrGradientEffect::CreateArgs(args.fContext, this, &matrix, fTileMode,
+                                     std::move(colorSpaceXform), SkToBool(args.fDstColorSpace))));
     return GrFragmentProcessor::MulOutputByInputAlpha(std::move(inner));
 }
 
 
 #endif
 
 #ifndef SK_IGNORE_TO_STRING
 void SkLinearGradient::toString(SkString* str) const {
     str->append("SkLinearGradient (");
 
@@ skipping 278 matching lines @@
             this->shade4_dx_clamp<false, true>(dstC, count, fx, dx, invDx, dither);
         }
     } else {
         if (fApplyAlphaAfterInterp) {
             this->shade4_dx_clamp<true, false>(dstC, count, fx, dx, invDx, dither);
         } else {
             this->shade4_dx_clamp<false, false>(dstC, count, fx, dx, invDx, dither);
         }
     }
 }