Add XferProcessor factory in GrPaint and GrDrawState.

src/gpu/effects/GrPorterDuffXferProcessor.h

Index: src/gpu/effects/GrPorterDuffXferProcessor.h
diff --git a/src/gpu/effects/GrPorterDuffXferProcessor.h b/src/gpu/effects/GrPorterDuffXferProcessor.h
new file mode 100644
index 0000000000000000000000000000000000000000..474285d829ea69c9dadc970a3d9dcfe474106c87
--- /dev/null
+++ b/src/gpu/effects/GrPorterDuffXferProcessor.h
@@ -0,0 +1,78 @@
+/*
+ * 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 GrPorterDuffXferProcessor_DEFINED
+#define GrPorterDuffXferProcessor_DEFINED
+
+#include "GrTypes.h"
+#include "GrXferProcessor.h"
+#include "SkXfermode.h"
+
+class GrBackendFragmentProcessorFactory;
+class GrDrawState;
+class GrGLPorterDuffXferProcessor;
+class GrInvariantOutput;
+
+class GrPorterDuffXferProcessor : public GrXferProcessor {
+public:
+    static GrXferProcessor* Create(GrBlendCoeff srcBlend, GrBlendCoeff dstBlend) {
+        return SkNEW_ARGS(GrPorterDuffXferProcessor, (srcBlend, dstBlend));
+    }
+
+    virtual ~GrPorterDuffXferProcessor();
+
+    virtual const GrBackendFragmentProcessorFactory& getFactory() const SK_OVERRIDE;
+
+    typedef GrGLPorterDuffXferProcessor GLProcessor;
+    static const char* Name() { return "Porter Duff"; }
+
+private:
+    GrPorterDuffXferProcessor(GrBlendCoeff srcBlend, GrBlendCoeff dstBlend);
+
+    virtual bool onIsEqual(const GrFragmentProcessor& fpBase) const SK_OVERRIDE {
+        const GrPorterDuffXferProcessor& xp = fpBase.cast<GrPorterDuffXferProcessor>();
+        if (fSrcBlend != xp.fSrcBlend || fDstBlend != xp.fDstBlend) {
+            return false;
+        }
+        return true;
+    }
+
+    virtual void onComputeInvariantOutput(GrInvariantOutput* inout) const SK_OVERRIDE;
+
+    GrBlendCoeff fSrcBlend;
+    GrBlendCoeff fDstBlend;
+    
+    typedef GrXferProcessor INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+class GrPorterDuffXPFactory : public GrXPFactory {
+public:
+    static GrXPFactory* Create(SkXfermode::Coeff src, SkXfermode::Coeff dst) {
+        return SkNEW_ARGS(GrPorterDuffXPFactory, ((GrBlendCoeff)(src), (GrBlendCoeff)(dst)));
+    }
+
+    static GrXPFactory* Create(GrBlendCoeff src, GrBlendCoeff dst) {
+        return SkNEW_ARGS(GrPorterDuffXPFactory, (src, dst));
+    }
+
+    const GrXferProcessor* createXferProcessor() const SK_OVERRIDE;
+
+    bool supportsRGBCoverage(GrColor knownColor, uint32_t knownColorFlags) const SK_OVERRIDE;
+
+private:
+    GrPorterDuffXPFactory(GrBlendCoeff src, GrBlendCoeff dst)
+        : fSrc(src), fDst(dst) {}
+
+    GrBlendCoeff fSrc;
+    GrBlendCoeff fDst;
+
+    typedef GrXPFactory INHERITED;
+};
+
+#endif