Added registerChild; transforms, textures, glKey automatically handled.

BUG=skia:

Review URL: https://codereview.chromium.org/1266633003
diff --git a/src/effects/gradients/SkRadialGradient.cpp b/src/effects/gradients/SkRadialGradient.cpp
index 1976382..4f97e26 100644
--- a/src/effects/gradients/SkRadialGradient.cpp
+++ b/src/effects/gradients/SkRadialGradient.cpp
@@ -468,11 +468,6 @@
 
     const char* name() const override { return "Radial Gradient"; }
 
-    virtual void getGLProcessorKey(const GrGLSLCaps& caps,
-                                   GrProcessorKeyBuilder* b) const override {
-        GrGLRadialGradient::GenKey(*this, caps, b);
-    }
-
     GrGLFragmentProcessor* createGLInstance() const override {
         return SkNEW_ARGS(GrGLRadialGradient, (*this));
     }
@@ -487,6 +482,11 @@
         this->initClassID<GrRadialGradient>();
     }
 
+    virtual void onGetGLProcessorKey(const GrGLSLCaps& caps,
+                                     GrProcessorKeyBuilder* b) const override {
+        GrGLRadialGradient::GenKey(*this, caps, b);
+    }
+
     GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
 
     typedef GrGradientEffect INHERITED;