Remove owning_id from EffectNode and replace it by an opaque stable_id

cc/blink/web_scrollbar_layer_impl.h

Index: cc/blink/web_scrollbar_layer_impl.h
diff --git a/cc/blink/web_scrollbar_layer_impl.h b/cc/blink/web_scrollbar_layer_impl.h
index 952277635c02f42e40e9cdc134355ba4914ccf1b..d7d52cad30d793d298c1a4ac7a994807db205c8e 100644
--- a/cc/blink/web_scrollbar_layer_impl.h
+++ b/cc/blink/web_scrollbar_layer_impl.h
@@ -38,6 +38,7 @@ class WebScrollbarLayerImpl : public blink::WebScrollbarLayer {
   // blink::WebScrollbarLayer implementation.
   blink::WebLayer* Layer() override;
   void SetScrollLayer(blink::WebLayer* layer) override;
+  void SetElementId(const cc::ElementId&) override;
 
  private:
   std::unique_ptr<WebLayerImpl> layer_;