Tweak a couple things I found confusing in ColorSpaceXform unit tests.

tests/ColorSpaceXformTest.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 "Resources.h"
 #include "SkCodec.h"
 #include "SkColorPriv.h"
 #include "SkColorSpace.h"
 #include "SkColorSpace_Base.h"
 #include "SkColorSpaceXform.h"
 #include "Test.h"
 
 class ColorSpaceXformTest {
 public:
-    static std::unique_ptr<SkColorSpaceXform> CreateDefaultXform(const sk_sp<SkGammas>& srcGamma,
-            const SkMatrix44& srcToDst, const sk_sp<SkGammas>& dstGamma) {
-
-        sk_sp<SkColorSpace> srcSpace(
-                new SkColorSpace_Base(nullptr, srcGamma, SkMatrix::I(), nullptr));
-        sk_sp<SkColorSpace> dstSpace(
-                new SkColorSpace_Base(nullptr, dstGamma, SkMatrix::I(), nullptr));
-
-        return SkColorSpaceXform::New(srcSpace, dstSpace);
+    static std::unique_ptr<SkColorSpaceXform> CreateIdentityXform(const sk_sp<SkGammas>& gammas) {
+        // Logically we can pass any matrix here.  For simplicty, pass I(), i.e. D50 XYZ gamut.
+        sk_sp<SkColorSpace> space(new SkColorSpace_Base(nullptr, gammas, SkMatrix::I(), nullptr));
+        return SkColorSpaceXform::New(space, space);
     }
 };
 
 static bool almost_equal(int x, int y) {
     return SkTAbs(x - y) <= 1;
 }
 
-static void test_xform(skiatest::Reporter* r, const sk_sp<SkGammas>& gammas) {
+static void test_identity_xform(skiatest::Reporter* r, const sk_sp<SkGammas>& gammas) {
     // Arbitrary set of 10 pixels
     constexpr int width = 10;
     constexpr uint32_t srcPixels[width] = {
             0xFFABCDEF, 0xFF146829, 0xFF382759, 0xFF184968, 0xFFDE8271,
             0xFF32AB52, 0xFF0383BC, 0xFF000102, 0xFFFFFFFF, 0xFFDDEEFF, };
     uint32_t dstPixels[width];
 
-    // Identity matrix
-    SkMatrix44 srcToDst = SkMatrix44::I();
-
-    // Create and perform xform
-    std::unique_ptr<SkColorSpaceXform> xform =
-            ColorSpaceXformTest::CreateDefaultXform(gammas, srcToDst, gammas);
+    // Create and perform an identity xform.
+    std::unique_ptr<SkColorSpaceXform> xform = ColorSpaceXformTest::CreateIdentityXform(gammas);
     xform->applyTo8888(dstPixels, srcPixels, width);
 
-    // Since the matrix is the identity, and the gamma curves match, the pixels
-    // should be unchanged.
+    // Since the src->dst matrix is the identity, and the gamma curves match,
+    // the pixels should be unchanged.
     for (int i = 0; i < width; i++) {
         REPORTER_ASSERT(r, almost_equal(((srcPixels[i] >>  0) & 0xFF),
                                         SkGetPackedR32(dstPixels[i])));
         REPORTER_ASSERT(r, almost_equal(((srcPixels[i] >>  8) & 0xFF),
                                         SkGetPackedG32(dstPixels[i])));
         REPORTER_ASSERT(r, almost_equal(((srcPixels[i] >> 16) & 0xFF),
                                         SkGetPackedB32(dstPixels[i])));
         REPORTER_ASSERT(r, almost_equal(((srcPixels[i] >> 24) & 0xFF),
                                         SkGetPackedA32(dstPixels[i])));
     }
@@ skipping 12 matching lines @@
     red.fTable[2] = green.fTable[2] = blue.fTable[2] = 0.10f;
     red.fTable[3] = green.fTable[3] = blue.fTable[3] = 0.15f;
     red.fTable[4] = green.fTable[4] = blue.fTable[4] = 0.25f;
     red.fTable[5] = green.fTable[5] = blue.fTable[5] = 0.35f;
     red.fTable[6] = green.fTable[6] = blue.fTable[6] = 0.45f;
     red.fTable[7] = green.fTable[7] = blue.fTable[7] = 0.60f;
     red.fTable[8] = green.fTable[8] = blue.fTable[8] = 0.75f;
     red.fTable[9] = green.fTable[9] = blue.fTable[9] = 1.00f;
     sk_sp<SkGammas> gammas =
             sk_make_sp<SkGammas>(std::move(red), std::move(green), std::move(blue));
-    test_xform(r, gammas);
+    test_identity_xform(r, gammas);
 }
 
 DEF_TEST(ColorSpaceXform_ParametricGamma, r) {
     // Parametric gamma curves
     SkGammaCurve red, green, blue;
 
     // Interval, switch xforms at 0.0031308f
     red.fD = green.fD = blue.fD = 0.04045f;
 
     // First equation:
     red.fE = green.fE = blue.fE = 1.0f / 12.92f;
 
     // Second equation:
     // Note that the function is continuous (it's actually sRGB).
     red.fA = green.fA = blue.fA = 1.0f / 1.055f;
     red.fB = green.fB = blue.fB = 0.055f / 1.055f;
     red.fC = green.fC = blue.fC = 0.0f;
     red.fG = green.fG = blue.fG = 2.4f;
     sk_sp<SkGammas> gammas =
             sk_make_sp<SkGammas>(std::move(red), std::move(green), std::move(blue));
-    test_xform(r, gammas);
+    test_identity_xform(r, gammas);
 }
 
 DEF_TEST(ColorSpaceXform_ExponentialGamma, r) {
     // Exponential gamma curves
     SkGammaCurve red, green, blue;
     red.fValue = green.fValue = blue.fValue = 1.4f;
     sk_sp<SkGammas> gammas =
             sk_make_sp<SkGammas>(std::move(red), std::move(green), std::move(blue));
-    test_xform(r, gammas);
+    test_identity_xform(r, gammas);
 }