Virtual Desks: Destroy any pending animations on shutdown

BUG=987868
TEST=Run ClusterFuzz Reproduce locally

Change-Id: I617ff4b44943aa10e957780bfcba6f69a6d485aa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1725510
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682365}

ash/shell.cc

@@ -595,6 +595,9 @@ Shell::~Shell() {
   for (auto& observer : shell_observers_)
     observer.OnShellDestroying();
 
+  if (features::IsVirtualDesksEnabled())
+    desks_controller_->Shutdown();
+
   // Wayland depends upon some ash specific objects. Destroy it early on.
   wayland_server_controller_.reset();
 

ash/wm/desks/desks_controller.cc

@@ -105,6 +105,10 @@ DesksController* DesksController::Get() {
   return Shell::Get()->desks_controller();
 }
 
+void DesksController::Shutdown() {
+  desk_switch_animators_.clear();
+}
+
 void DesksController::AddObserver(Observer* observer) {
   observers_.AddObserver(observer);
 }

ash/wm/desks/desks_controller.h

@@ -64,6 +64,9 @@ class ASH_EXPORT DesksController
 
   const Desk* active_desk() const { return active_desk_; }
 
+  // Destroys any pending animations in preparation for shutdown.
+  void Shutdown();
+
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);