Create xfer processor backend.

include/gpu/GrXferProcessor.h

Index: include/gpu/GrXferProcessor.h
diff --git a/include/gpu/GrXferProcessor.h b/include/gpu/GrXferProcessor.h
index b7d0bdd9fa9ef7717471a3857b9e788e95793378..696359b8b3fb351438c3d0b816e802a23422725f 100644
--- a/include/gpu/GrXferProcessor.h
+++ b/include/gpu/GrXferProcessor.h
@@ -9,10 +9,13 @@
 #define GrXferProcessor_DEFINED
 
 #include "GrColor.h"
-#include "GrFragmentProcessor.h"
+#include "GrProcessor.h"
 #include "GrTypes.h"
 #include "SkXfermode.h"
 
+class GrDrawTargetCaps;
+class GrGLCaps;
+class GrGLXferProcessor;
 class GrProcOptInfo;
 
 /**
@@ -28,9 +31,21 @@ class GrProcOptInfo;
  * A GrXferProcessor is never installed directly into our draw state, but instead is created from a
  * GrXPFactory once we have finalized the state of our draw.
  */
-class GrXferProcessor : public GrFragmentProcessor {
+class GrXferProcessor : public GrProcessor {
 public:
     /**
+     * Sets a unique key on the GrProcessorKeyBuilder that is directly associated with this xfer
+     * processor's GL backend implementation.
+     */
+    virtual void getGLProcessorKey(const GrGLCaps& caps,
+                                   GrProcessorKeyBuilder* b) const = 0;
+
+    /** Returns a new instance of the appropriate *GL* implementation class
+        for the given GrXferProcessor; caller is responsible for deleting
+        the object. */
+    virtual GrGLXferProcessor* createGLInstance() const = 0;
+
+    /**
      * Optimizations for blending / coverage that an OptDrawState should apply to itself.
      */
     enum OptFlags {
@@ -74,7 +89,8 @@ public:
                                       bool colorWriteDisabled,
                                       bool doesStencilWrite,
                                       GrColor* color,
-                                      uint8_t* coverage) = 0;
+                                      uint8_t* coverage,
+                                      const GrDrawTargetCaps& caps) = 0;
 
     struct BlendInfo {
         GrBlendCoeff fSrcBlend;
@@ -87,6 +103,27 @@ public:
     /** Will this prceossor read the destination pixel value? */
     bool willReadDstColor() const { return fWillReadDstColor; }
 
+    /** 
+     * Returns whether or not this xferProcossor will set a secondary output to be used with dual
+     * source blending.
+     */
+    virtual bool hasSecondaryOutput() const { return false; }
+
+    /** Returns true if this and other processor conservatively draw identically. It can only return
+        true when the two processor are of the same subclass (i.e. they return the same object from
+        from getFactory()).
+
+        A return value of true from isEqual() should not be used to test whether the processor would
+        generate the same shader code. To test for identical code generation use getGLProcessorKey*/
+    
+    bool isEqual(const GrXferProcessor& that) const {
+        if (this->classID() != that.classID()) {
+            return false;
+        }
+        return this->onIsEqual(that);
+    }
+   
+
 protected:
     GrXferProcessor() : fWillReadDstColor(false) {}
 
@@ -98,6 +135,7 @@ protected:
     void setWillReadDstColor() { fWillReadDstColor = true; }
 
 private:
+    virtual bool onIsEqual(const GrXferProcessor&) const = 0;
 
     bool         fWillReadDstColor;