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 4bc3dd019b553895c1c28e5bf434b01213455fad..ca4fa2459f97a1c1ca9b823120fae1d2bdcfeafa 100644
--- a/src/gpu/gl/GrGLProcessor.h
+++ b/src/gpu/gl/GrGLProcessor.h
@@ -125,4 +125,16 @@ private:
     typedef GrGLProcessor INHERITED;
 };
 
+class GrGLXferProcessor : public GrGLFragmentProcessor {
+public:
+    GrGLXferProcessor(const GrBackendProcessorFactory& factory)
+        : INHERITED(factory) {
+    }
+    
+    virtual ~GrGLXferProcessor() {}
+
+private:
+    typedef GrGLFragmentProcessor INHERITED;
+};
+
 #endif