Added tree structure to GrGLFragmentProcessor, i.e. GL instances

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 2a4006bf6739bcfc926fb974c197686525bbf9f7..05e07b64ced3035e1c8979067b0aa4d7094ac7dc 100644
--- a/src/gpu/effects/GrCustomXfermodePriv.h
+++ b/src/gpu/effects/GrCustomXfermodePriv.h
@@ -29,14 +29,14 @@ class GrCustomXferFP : public GrFragmentProcessor {
 public:
     GrCustomXferFP(GrProcessorDataManager*, SkXfermode::Mode mode, GrTexture* background);
 
-    GrGLFragmentProcessor* createGLInstance() const override;
-
     const char* name() const override { return "Custom Xfermode"; }
 
     SkXfermode::Mode mode() const { return fMode; }
     const GrTextureAccess&  backgroundAccess() const { return fBackgroundAccess; }
 
 private:
+    GrGLFragmentProcessor* onCreateGLInstance() const override;
+
     void onGetGLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override;
 
     bool onIsEqual(const GrFragmentProcessor& other) const override;