Revert of Revert of Move DstCopy on gpu into the GrXferProcessor.

include/gpu/effects/GrPorterDuffXferProcessor.h

Index: include/gpu/effects/GrPorterDuffXferProcessor.h
diff --git a/include/gpu/effects/GrPorterDuffXferProcessor.h b/include/gpu/effects/GrPorterDuffXferProcessor.h
index af10fa23ec1fbff1b51d3cdc993bee4b120b48f9..e47ec1e9048b9d3cd4de3863362a69cdcfce7853 100644
--- a/include/gpu/effects/GrPorterDuffXferProcessor.h
+++ b/include/gpu/effects/GrPorterDuffXferProcessor.h
@@ -12,20 +12,21 @@
 #include "GrXferProcessor.h"
 #include "SkXfermode.h"
 
+class GrDrawTargetCaps;
 class GrProcOptInfo;
 
 class GrPorterDuffXferProcessor : public GrXferProcessor {
 public:
     static GrXferProcessor* Create(GrBlendCoeff srcBlend, GrBlendCoeff dstBlend,
-                                   GrColor constant = 0) {
-        return SkNEW_ARGS(GrPorterDuffXferProcessor, (srcBlend, dstBlend, constant));
+                                   GrColor constant, const GrDeviceCoordTexture* dstCopy,
+                                   bool willReadDstColor) {
+        return SkNEW_ARGS(GrPorterDuffXferProcessor, (srcBlend, dstBlend, constant, dstCopy,
+                                                      willReadDstColor));
     }
 
     ~GrPorterDuffXferProcessor() SK_OVERRIDE;
 
     const char* name() const SK_OVERRIDE { return "Porter Duff"; }
-
-    void getGLProcessorKey(const GrGLCaps& caps, GrProcessorKeyBuilder* b) const SK_OVERRIDE;
 
     GrGLXferProcessor* createGLInstance() const SK_OVERRIDE;
 
@@ -75,7 +76,10 @@
     }
 
 private:
-    GrPorterDuffXferProcessor(GrBlendCoeff srcBlend, GrBlendCoeff dstBlend, GrColor constant);
+    GrPorterDuffXferProcessor(GrBlendCoeff srcBlend, GrBlendCoeff dstBlend, GrColor constant,
+                              const GrDeviceCoordTexture* dstCopy, bool willReadDstColor);
+
+    void onGetGLProcessorKey(const GrGLCaps& caps, GrProcessorKeyBuilder* b) const SK_OVERRIDE;
 
     bool onIsEqual(const GrXferProcessor& xpBase) const SK_OVERRIDE {
         const GrPorterDuffXferProcessor& xp = xpBase.cast<GrPorterDuffXferProcessor>();
@@ -119,9 +123,6 @@
         return SkNEW_ARGS(GrPorterDuffXPFactory, (src, dst));
     }
 
-    GrXferProcessor* createXferProcessor(const GrProcOptInfo& colorPOI,
-                                         const GrProcOptInfo& coveragePOI) const SK_OVERRIDE;
-
     bool supportsRGBCoverage(GrColor knownColor, uint32_t knownColorFlags) const SK_OVERRIDE;
 
     bool canApplyCoverage(const GrProcOptInfo& colorPOI,
@@ -132,10 +133,14 @@
     void getInvariantOutput(const GrProcOptInfo& colorPOI, const GrProcOptInfo& coveragePOI,
                             GrXPFactory::InvariantOutput*) const SK_OVERRIDE;
 
-    bool willReadDst() const SK_OVERRIDE { return false; }
-
 private:
     GrPorterDuffXPFactory(GrBlendCoeff src, GrBlendCoeff dst); 
+
+    GrXferProcessor* onCreateXferProcessor(const GrProcOptInfo& colorPOI,
+                                           const GrProcOptInfo& coveragePOI,
+                                           const GrDeviceCoordTexture* dstCopy) const SK_OVERRIDE;
+
+    bool willReadDstColor() const SK_OVERRIDE;
 
     bool onIsEqual(const GrXPFactory& xpfBase) const SK_OVERRIDE {
         const GrPorterDuffXPFactory& xpf = xpfBase.cast<GrPorterDuffXPFactory>();