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

src/effects/gradients/SkLinearGradient.cpp

Index: src/effects/gradients/SkLinearGradient.cpp
diff --git a/src/effects/gradients/SkLinearGradient.cpp b/src/effects/gradients/SkLinearGradient.cpp
index 7ca1b604209c61735c0a0fbc6b0999d8c5cf18dd..fb0aa9836aab16333677ec8d07fd67eccb572238 100644
--- a/src/effects/gradients/SkLinearGradient.cpp
+++ b/src/effects/gradients/SkLinearGradient.cpp
@@ -495,10 +495,6 @@ public:
 
     const char* name() const override { return "Linear Gradient"; }
 
-    GrGLFragmentProcessor* createGLInstance() const override {
-        return SkNEW_ARGS(GrGLLinearGradient, (*this));
-    }
-
 private:
     GrLinearGradient(GrContext* ctx,
                      GrProcessorDataManager* procDataManager,
@@ -509,6 +505,10 @@ private:
         this->initClassID<GrLinearGradient>();
     }
 
+    GrGLFragmentProcessor* onCreateGLInstance() const override {
+        return SkNEW_ARGS(GrGLLinearGradient, (*this));
+    }
+
     virtual void onGetGLProcessorKey(const GrGLSLCaps& caps,
                                      GrProcessorKeyBuilder* b) const override {
         GrGLLinearGradient::GenKey(*this, caps, b);