Remove owning_id from EffectNode and replace it by an opaque stable_id

cc/input/scrollbar_animation_controller.cc

Index: cc/input/scrollbar_animation_controller.cc
diff --git a/cc/input/scrollbar_animation_controller.cc b/cc/input/scrollbar_animation_controller.cc
index 14dfe30a5ef5312c4bc693260022cea074e493c5..1f066dbc610944779ae68a55a25427e0b404448c 100644
--- a/cc/input/scrollbar_animation_controller.cc
+++ b/cc/input/scrollbar_animation_controller.cc
@@ -164,6 +164,7 @@ void ScrollbarAnimationController::RunAnimationFrame(float progress) {
     opacity = std::min(1.f - progress, opacity_);
   }
 
+  NotifyScrollbarLayersOfOpacityAnimation(opacity);
   ApplyOpacityToScrollbars(opacity);
   if (progress == 1.f)
     StopAnimation();
@@ -330,16 +331,20 @@ bool ScrollbarAnimationController::Captured() const {
 
 void ScrollbarAnimationController::Show() {
   delayed_scrollbar_animation_.Cancel();
+  NotifyScrollbarLayersOfOpacityAnimation(1.0f);
   ApplyOpacityToScrollbars(1.0f);
 }
 
-void ScrollbarAnimationController::ApplyOpacityToScrollbars(float opacity) {
+void ScrollbarAnimationController::NotifyScrollbarLayersOfOpacityAnimation(
+    float opacity) {
   for (ScrollbarLayerImplBase* scrollbar : Scrollbars()) {
     DCHECK(scrollbar->is_overlay_scrollbar());
     float effective_opacity = scrollbar->CanScrollOrientation() ? opacity : 0;
     scrollbar->SetOverlayScrollbarLayerOpacityAnimated(effective_opacity);
   }
+}
 
+void ScrollbarAnimationController::ApplyOpacityToScrollbars(float opacity) {
   bool previouslyVisible = opacity_ > 0.0f;
   bool currentlyVisible = opacity > 0.0f;