Use SkXfermode as public facing enum for GrPorterDuffXP

include/gpu/GrXferProcessor.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrXferProcessor_DEFINED
 #define GrXferProcessor_DEFINED
 
 #include "GrColor.h"
 #include "GrProcessor.h"
 #include "GrTexture.h"
 #include "GrTypes.h"
 #include "SkXfermode.h"
 
 class GrDrawTargetCaps;
 class GrGLCaps;
 class GrGLXferProcessor;
 class GrProcOptInfo;
 
 /**
+ * Coeffecients for alpha-blending.
+ */
+enum GrBlendCoeff {
+    kInvalid_GrBlendCoeff = -1,
+
+    kZero_GrBlendCoeff,    //<! 0
+    kOne_GrBlendCoeff,     //<! 1
+    kSC_GrBlendCoeff,      //<! src color
+    kISC_GrBlendCoeff,     //<! one minus src color
+    kDC_GrBlendCoeff,      //<! dst color
+    kIDC_GrBlendCoeff,     //<! one minus dst color
+    kSA_GrBlendCoeff,      //<! src alpha
+    kISA_GrBlendCoeff,     //<! one minus src alpha
+    kDA_GrBlendCoeff,      //<! dst alpha
+    kIDA_GrBlendCoeff,     //<! one minus dst alpha
+    kConstC_GrBlendCoeff,  //<! constant color
+    kIConstC_GrBlendCoeff, //<! one minus constant color
+    kConstA_GrBlendCoeff,  //<! constant color alpha
+    kIConstA_GrBlendCoeff, //<! one minus constant color alpha
+    kS2C_GrBlendCoeff,

[bsalomon, 2015/02/14 20:45:59]

if any of these need comments its the S2 guys :)

+    kIS2C_GrBlendCoeff,
+    kS2A_GrBlendCoeff,
+    kIS2A_GrBlendCoeff,
+
+    kTotalGrBlendCoeffCount
+};
+
+/**
  * GrXferProcessor is responsible for implementing the xfer mode that blends the src color and dst
  * color. It does this by emitting fragment shader code and controlling the fixed-function blend
  * state. The inputs to its shader code are the final computed src color and fractional pixel
  * coverage. The GrXferProcessor's shader code writes the fragment shader output color that goes
  * into the fixed-function blend. When dual-source blending is available, it may also write a
  * seconday fragment shader output color. When allowed by the backend API, the GrXferProcessor may
  * read the destination color. The GrXferProcessor is responsible for setting the blend coefficients
  * and blend constant color.
  *
  * A GrXferProcessor is never installed directly into our draw state, but instead is created from a
@@ skipping 255 matching lines @@
     enum {
         kIllegalXPFClassID = 0,
     };
     static int32_t gCurrXPFClassID;
 
     typedef GrProgramElement INHERITED;
 };
 
 #endif