Prevent hiding a toast during animation

ash/system/toast/toast_overlay.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/system/toast/toast_overlay.h"
 
 #include "ash/common/shelf/wm_shelf.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/wm_root_window_controller.h"
 #include "ash/common/wm_shell.h"
@@ skipping 233 matching lines @@
 ToastOverlay::~ToastOverlay() {
   overlay_widget_->Close();
 }
 
 void ToastOverlay::Show(bool visible) {
   if (overlay_widget_->GetLayer()->GetTargetVisibility() == visible)
     return;
 
   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);
   // ScopedLayerAnimationSettings ctor chanes the transition duration, so change
   // back it to the original value (should be zero).
   animation_settings.SetTransitionDuration(original_duration);
 
   animation_settings.AddObserver(this);
 
   if (visible) {
@@ skipping 23 matching lines @@
 
 views::Widget* ToastOverlay::widget_for_testing() {
   return overlay_widget_.get();
 }
 
 void ToastOverlay::ClickDismissButtonForTesting(const ui::Event& event) {
   overlay_view_->button()->NotifyClick(event);
 }
 
 }  // namespace ash