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

src/gpu/effects/GrCustomXfermodePriv.h

Index: src/gpu/effects/GrCustomXfermodePriv.h
diff --git a/src/gpu/effects/GrCustomXfermodePriv.h b/src/gpu/effects/GrCustomXfermodePriv.h
index 45a9d3005db94afc43f793006d4cd3215c4d3f6b..681c805ba7034c9eea960f5bee88c596cd98a32e 100644
--- a/src/gpu/effects/GrCustomXfermodePriv.h
+++ b/src/gpu/effects/GrCustomXfermodePriv.h
@@ -9,6 +9,7 @@
 #define GrCustomXfermodePriv_DEFINED
 
 #include "GrCoordTransform.h"
+#include "GrDrawTargetCaps.h"
 #include "GrFragmentProcessor.h"
 #include "GrTextureAccess.h"
 #include "GrXferProcessor.h"
@@ -57,19 +58,18 @@
 
 class GrCustomXP : public GrXferProcessor {
 public:
-    static GrXferProcessor* Create(SkXfermode::Mode mode) {
+    static GrXferProcessor* Create(SkXfermode::Mode mode, const GrDeviceCoordTexture* dstCopy,
+                                   bool willReadDstColor) {
         if (!GrCustomXfermode::IsSupportedMode(mode)) {
             return NULL;
         } else {
-            return SkNEW_ARGS(GrCustomXP, (mode));
+            return SkNEW_ARGS(GrCustomXP, (mode, dstCopy, willReadDstColor));
         }
     }
 
     ~GrCustomXP() SK_OVERRIDE {};
 
     const char* name() const SK_OVERRIDE { return "Custom Xfermode"; }
-
-    void getGLProcessorKey(const GrGLCaps& caps, GrProcessorKeyBuilder* b) const SK_OVERRIDE;
 
     GrGLXferProcessor* createGLInstance() const SK_OVERRIDE;
 
@@ -90,7 +90,9 @@
     SkXfermode::Mode mode() const { return fMode; }
 
 private:
-    GrCustomXP(SkXfermode::Mode mode);
+    GrCustomXP(SkXfermode::Mode mode, const GrDeviceCoordTexture* dstCopy, bool willReadDstColor);
+
+    void onGetGLProcessorKey(const GrGLCaps& caps, GrProcessorKeyBuilder* b) const SK_OVERRIDE;
 
     bool onIsEqual(const GrXferProcessor& xpBase) const SK_OVERRIDE;
 
@@ -104,11 +106,6 @@
 class GrCustomXPFactory : public GrXPFactory {
 public:
     GrCustomXPFactory(SkXfermode::Mode mode); 
-
-    GrXferProcessor* createXferProcessor(const GrProcOptInfo& colorPOI,
-                                         const GrProcOptInfo& coveragePOI) const SK_OVERRIDE {
-        return GrCustomXP::Create(fMode);
-    }
 
     bool supportsRGBCoverage(GrColor knownColor, uint32_t knownColorFlags) const SK_OVERRIDE {
         return true;
@@ -126,9 +123,15 @@
     void getInvariantOutput(const GrProcOptInfo& colorPOI, const GrProcOptInfo& coveragePOI,
                             GrXPFactory::InvariantOutput*) const SK_OVERRIDE;
 
-    bool willReadDst() const SK_OVERRIDE { return true; }
+private:
+    GrXferProcessor* onCreateXferProcessor(const GrProcOptInfo& colorPOI,
+                                           const GrProcOptInfo& coveragePOI,
+                                           const GrDeviceCoordTexture* dstCopy) const SK_OVERRIDE {
+        return GrCustomXP::Create(fMode, dstCopy, this->willReadDstColor());
+    }
 
-private:
+    bool willReadDstColor() const SK_OVERRIDE { return true; }
+
     bool onIsEqual(const GrXPFactory& xpfBase) const SK_OVERRIDE {
         const GrCustomXPFactory& xpf = xpfBase.cast<GrCustomXPFactory>();
         return fMode == xpf.fMode;