Move Gpu ArithmeticMode xfer effect to _gpu files.

src/effects/SkArithmeticMode_gpu.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkArithmeticMode_gpu_DEFINED
+#define SkArithmeticMode_gpu_DEFINED
+
+#if SK_SUPPORT_GPU
+
+#include "GrCoordTransform.h"
+#include "GrFragmentProcessor.h"
+#include "GrTextureAccess.h"
+
+class GrInvariantOutput;
+class GrTexture;
+
+///////////////////////////////////////////////////////////////////////////////
+// Fragment Processor
+///////////////////////////////////////////////////////////////////////////////
+
+class GrGLArtithmeticFP;
+
+class GrArithmeticFP : public GrFragmentProcessor {
+public:
+    static GrFragmentProcessor* Create(float k1, float k2, float k3, float k4, bool enforcePMColor,
+                               GrTexture* background) {
+        return SkNEW_ARGS(GrArithmeticFP, (k1, k2, k3, k4, enforcePMColor, background));
+    }
+
+    ~GrArithmeticFP() SK_OVERRIDE {};
+
+    const char* name() const SK_OVERRIDE { return "Arithmetic"; }
+
+    void getGLProcessorKey(const GrGLCaps& caps, GrProcessorKeyBuilder* b) const SK_OVERRIDE;
+
+    GrGLFragmentProcessor* createGLInstance() const SK_OVERRIDE;
+
+    GrTexture* backgroundTexture() const { return fBackgroundAccess.getTexture(); }
+
+    float k1() const { return fK1; }
+    float k2() const { return fK2; }
+    float k3() const { return fK3; }
+    float k4() const { return fK4; }
+    bool enforcePMColor() const { return fEnforcePMColor; }
+
+private:
+    bool onIsEqual(const GrFragmentProcessor&) const SK_OVERRIDE;
+
+    void onComputeInvariantOutput(GrInvariantOutput* inout) const SK_OVERRIDE;
+
+    GrArithmeticFP(float k1, float k2, float k3, float k4, bool enforcePMColor,
+                   GrTexture* background);
+    float                       fK1, fK2, fK3, fK4;

[bsalomon, 2015/01/14 15:25:31]

tiny nit, could you add a blank line before the vars?

+    bool                        fEnforcePMColor;
+    GrCoordTransform            fBackgroundTransform;
+    GrTextureAccess             fBackgroundAccess;
+
+    GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
+    typedef GrFragmentProcessor INHERITED;
+

[bsalomon, 2015/01/14 15:25:31]

extra \n here.

+};
+
+#endif
+#endif