Add color gamut xform helpers to GrGLSLShaderBuilder

include/gpu/GrColorSpaceXform.h

 /*
  * 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 GrColorSpaceXform_DEFINED
 #define GrColorSpaceXform_DEFINED
 
+#include "SkImageInfo.h"
 #include "SkRefCnt.h"
 
 class SkColorSpace;
 class SkMatrix44;
 
  /**
   * Represents a color gamut transformation (as a 4x4 color matrix)
   */
 class GrColorSpaceXform : public SkRefCnt {
 public:
-    GrColorSpaceXform(const SkMatrix44& srcToDst);
+    GrColorSpaceXform(const SkMatrix44& srcToDst, SkAlphaType srcAlphaType);
 
-    static sk_sp<GrColorSpaceXform> Make(SkColorSpace* src, SkColorSpace* dst);
+    static sk_sp<GrColorSpaceXform> Make(SkColorSpace* src, SkColorSpace* dst,
+                                         SkAlphaType srcAlphaType);
 
     const float* srcToDst() { return fSrcToDst; }
+    SkAlphaType alphaType() const { return fSrcAlphaType; }
+
+    /**
+     * GrGLSLFragmentProcessor::GenKey() must call this and include the returned value in its

[bsalomon, 2016/09/07 14:46:37]

The GrGLSLFragmentProcessor::GenKey() thing is sort of a weird pattern many but
not all classes follow. The real method is
GrFragmentProcessor::getGLSLProcessorKey().

+     * computed key.
+     */
+    static uint32_t XformKey(GrColorSpaceXform* xform) {
+        if (!xform) {
+            return 0;
+        }
+        // Code generation just depends on whether the alpha type is premul or not
+        return kPremul_SkAlphaType == xform->fSrcAlphaType ? 1 : 2;
+    }
 
 private:
     // We store the column-major form of the srcToDst matrix, for easy uploading to uniforms
     float fSrcToDst[16];
+
+    // Alpha type of the source. If it's premul, we need special handling
+    SkAlphaType fSrcAlphaType;
 };
 
 #endif