When getGLInstance is called on a frag proc, the resulting GrGLFragmentProcessor will be the root of a tree of GrGLFragmentProcessors that mirrors the GrFragmentProcessor's tree. This allows setData() to be called recursively (removing the responsibility from compose shader) and allows gl instances direct access to their children gl instances so they can emit their code.

BUG=skia:4182

Review URL: https://codereview.chromium.org/1287023009
diff --git a/src/effects/gradients/SkRadialGradient.cpp b/src/effects/gradients/SkRadialGradient.cpp
index 4f97e26..4ff635a 100644
--- a/src/effects/gradients/SkRadialGradient.cpp
+++ b/src/effects/gradients/SkRadialGradient.cpp
@@ -468,10 +468,6 @@
 
     const char* name() const override { return "Radial Gradient"; }
 
-    GrGLFragmentProcessor* createGLInstance() const override {
-        return SkNEW_ARGS(GrGLRadialGradient, (*this));
-    }
-
 private:
     GrRadialGradient(GrContext* ctx,
                      GrProcessorDataManager* procDataManager,
@@ -482,6 +478,10 @@
         this->initClassID<GrRadialGradient>();
     }
 
+    GrGLFragmentProcessor* onCreateGLInstance() const override {
+        return SkNEW_ARGS(GrGLRadialGradient, (*this));
+    }
+
     virtual void onGetGLProcessorKey(const GrGLSLCaps& caps,
                                      GrProcessorKeyBuilder* b) const override {
         GrGLRadialGradient::GenKey(*this, caps, b);