Add SkColorSpaceXform to the public API

src/core/SkColorSpaceXform_Base.h

Index: src/core/SkColorSpaceXform_Base.h
diff --git a/src/core/SkColorSpaceXform_Base.h b/src/core/SkColorSpaceXform_Base.h
new file mode 100644
index 0000000000000000000000000000000000000000..02714ad59ee4800a9c5960aafd0ef72283375b08
--- /dev/null
+++ b/src/core/SkColorSpaceXform_Base.h
@@ -0,0 +1,62 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkColorSpaceXform_Base_DEFINED
+#define SkColorSpaceXform_Base_DEFINED
+
+#include "SkColorSpace.h"
+#include "SkColorSpace_Base.h"
+#include "SkColorSpaceXform.h"
+
+enum SrcGamma {
+    kLinear_SrcGamma,
+    kTable_SrcGamma,
+};
+
+enum DstGamma {
+    kLinear_DstGamma,
+    kSRGB_DstGamma,
+    k2Dot2_DstGamma,
+    kTable_DstGamma,
+};
+
+enum ColorSpaceMatch {
+    kNone_ColorSpaceMatch,
+    kGamut_ColorSpaceMatch,
+    kFull_ColorSpaceMatch,
+};
+
+template <SrcGamma kSrc, DstGamma kDst, ColorSpaceMatch kCSM>
+class SkColorSpaceXform_Base : public SkColorSpaceXform {
+public:
+    static constexpr int kDstGammaTableSize = 1024;
+
+protected:
+    bool onApply(ColorFormat dstFormat, void* dst, ColorFormat srcFormat, const void* src,
+                 int count, SkAlphaType alphaType) const override;
+
+private:
+    SkColorSpaceXform_Base(SkColorSpace* srcSpace, const SkMatrix44& srcToDst,
+                           SkColorSpace* dstSpace);
+
+    sk_sp<SkColorLookUpTable> fColorLUT;
+
+    // Contain pointers into storage or pointers into precomputed tables.
+    const float*              fSrcGammaTables[3];
+    const uint8_t*            fDstGammaTables[3];
+    SkAutoMalloc              fStorage;
+
+    float                     fSrcToDst[16];
+
+    friend class SkColorSpaceXform;
+    friend std::unique_ptr<SkColorSpaceXform> SlowIdentityXform(SkColorSpace* space);
+};
+
+// For testing.  Bypasses opts for when src and dst color spaces are equal.
+std::unique_ptr<SkColorSpaceXform> SlowIdentityXform(SkColorSpace* space);
+
+#endif