Prevent hiding a toast during animation

ash/common/system/toast/toast_overlay.cc

Index: ash/common/system/toast/toast_overlay.cc
diff --git a/ash/common/system/toast/toast_overlay.cc b/ash/common/system/toast/toast_overlay.cc
index 87d49c687e703ab71e236c569190dc65a394d786..868834144974974ef1a097a16d19d23660aec867 100644
--- a/ash/common/system/toast/toast_overlay.cc
+++ b/ash/common/system/toast/toast_overlay.cc
@@ -253,6 +253,13 @@ void ToastOverlay::Show(bool visible) {
 
   ui::LayerAnimator* animator = overlay_widget_->GetLayer()->GetAnimator();
   DCHECK(animator);
+  if (animator->is_animating()) {
+    // Showing during hiding animation doesn't happen since, ToastOverlay should
+    // be one-time-use and not be reused.
+    DCHECK(!visible);
+
+    return;
+  }
 
   base::TimeDelta original_duration = animator->GetTransitionDuration();
   ui::ScopedLayerAnimationSettings animation_settings(animator);