Add XferProcessor factory in GrPaint and GrDrawState.

src/gpu/gl/GrGLProcessor.h

Index: src/gpu/gl/GrGLProcessor.h
diff --git a/src/gpu/gl/GrGLProcessor.h b/src/gpu/gl/GrGLProcessor.h
index f5ebf51b089a27adf481f44c3f1cae061a0b24fe..f4caceae9c6f487b3996d03a7548ad626e2f5cbc 100644
--- a/src/gpu/gl/GrGLProcessor.h
+++ b/src/gpu/gl/GrGLProcessor.h
@@ -126,4 +126,16 @@ private:
     typedef GrGLProcessor INHERITED;
 };
 
+class GrGLXferProcessor : public GrGLFragmentProcessor {
+public:
+    GrGLXferProcessor(const GrBackendProcessorFactory& factory)
+        : INHERITED(factory) {
+    }
+    
+    virtual ~GrGLXferProcessor() {}
+
+private:
+    typedef GrGLFragmentProcessor INHERITED;
+};
+
 #endif