Cache the inverse matrix on SkColorSpace. Rename xyz() to toXYZ().

src/core/SkColorSpace.cpp

Index: src/core/SkColorSpace.cpp
diff --git a/src/core/SkColorSpace.cpp b/src/core/SkColorSpace.cpp
index e6676066bb24beac7ee8125478d1715921829fb9..9f04de0537f852ee744a69f0ad9cbb848d6a2a3d 100644
--- a/src/core/SkColorSpace.cpp
+++ b/src/core/SkColorSpace.cpp
@@ -19,6 +19,7 @@ SkColorSpace_Base::SkColorSpace_Base(SkGammaNamed gammaNamed, const SkMatrix44&
     , fGammaNamed(gammaNamed)
     , fGammas(nullptr)
     , fProfileData(nullptr)
+    , fFromXYZD50(SkMatrix44::kUninitialized_Constructor)
 {}
 
 SkColorSpace_Base::SkColorSpace_Base(sk_sp<SkColorLookUpTable> colorLUT, SkGammaNamed gammaNamed,
@@ -29,6 +30,7 @@ SkColorSpace_Base::SkColorSpace_Base(sk_sp<SkColorLookUpTable> colorLUT, SkGamma
     , fGammaNamed(gammaNamed)
     , fGammas(std::move(gammas))
     , fProfileData(std::move(profileData))
+    , fFromXYZD50(SkMatrix44::kUninitialized_Constructor)
 {}
 
 static constexpr float gSRGB_toXYZD50[] {
@@ -182,6 +184,20 @@ bool SkColorSpace::gammaIsLinear() const {
     return kLinear_SkGammaNamed == as_CSB(this)->fGammaNamed;
 }
 
+const SkMatrix44& SkColorSpace_Base::fromXYZD50() const {
+    fFromXYZOnce([this] {
+        if (!fToXYZD50.invert(&fFromXYZD50)) {
+            // If a client gives us a dst gamut with a transform that we can't invert, we will
+            // simply give them back a transform to sRGB gamut.
+            SkDEBUGFAIL("Non-invertible XYZ matrix, defaulting to sRGB");
+            SkMatrix44 srgbToxyzD50(SkMatrix44::kUninitialized_Constructor);
+            srgbToxyzD50.set3x3RowMajorf(gSRGB_toXYZD50);
+            srgbToxyzD50.invert(&fFromXYZD50);
+        }
+    });
+    return fFromXYZD50;
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
 enum Version {