Add color gamut xform helpers to GrGLSLShaderBuilder

src/gpu/GrColorSpaceXform.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrColorSpaceXform.h"
 #include "SkColorSpace.h"
 #include "SkMatrix44.h"
@@ skipping 16 matching lines @@
         sk_float_almost_equals(m.getFloat(2, 0), 0.0f, tol) &&
         sk_float_almost_equals(m.getFloat(2, 1), 0.0f, tol) &&
         sk_float_almost_equals(m.getFloat(2, 2), 1.0f, tol) &&
         sk_float_almost_equals(m.getFloat(2, 3), 0.0f, tol) &&
         sk_float_almost_equals(m.getFloat(3, 0), 0.0f, tol) &&
         sk_float_almost_equals(m.getFloat(3, 1), 0.0f, tol) &&
         sk_float_almost_equals(m.getFloat(3, 2), 0.0f, tol) &&
         sk_float_almost_equals(m.getFloat(3, 3), 1.0f, tol);
 }
 
-GrColorSpaceXform::GrColorSpaceXform(const SkMatrix44& srcToDst) {
+GrColorSpaceXform::GrColorSpaceXform(const SkMatrix44& srcToDst, SkAlphaType srcAlphaType)
+    : fSrcAlphaType(srcAlphaType) {
     srcToDst.asColMajorf(fSrcToDst);
 }
 
-sk_sp<GrColorSpaceXform> GrColorSpaceXform::Make(SkColorSpace* src, SkColorSpace* dst) {
+sk_sp<GrColorSpaceXform> GrColorSpaceXform::Make(SkColorSpace* src, SkColorSpace* dst,
+                                                 SkAlphaType srcAlphaType) {
     if (!src || !dst) {
         // Invalid
         return nullptr;
     }
 
     if (src == dst) {
         // Quick equality check - no conversion needed in this case
         return nullptr;
     }
 
     SkMatrix44 srcToDst(SkMatrix44::kUninitialized_Constructor);
     if (!dst->xyz().invert(&srcToDst)) {
         return nullptr;
     }
     srcToDst.postConcat(src->xyz());
 
     if (matrix_is_almost_identity(srcToDst)) {
         return nullptr;
     }
 
-    return sk_make_sp<GrColorSpaceXform>(srcToDst);
+    return sk_make_sp<GrColorSpaceXform>(srcToDst, srcAlphaType);
 }