Fix crash during shutdown

athena/screen/screen_manager_impl.cc

Index: athena/screen/screen_manager_impl.cc
diff --git a/athena/screen/screen_manager_impl.cc b/athena/screen/screen_manager_impl.cc
index c8395a7590d3d9b205744d86cd97e99dd7bed749..0b9f67e10079de23282d1b28b0af1d83e7f749de 100644
--- a/athena/screen/screen_manager_impl.cc
+++ b/athena/screen/screen_manager_impl.cc
@@ -240,6 +240,13 @@ ScreenManagerImpl::~ScreenManagerImpl() {
   root_window_->RemovePreTargetHandler(focus_controller);
   aura::client::SetActivationClient(root_window_, NULL);
   aura::client::SetFocusClient(root_window_, NULL);
+  aura::Window::Windows children = root_window_->children();
+  // Close All children:
+  for (aura::Window::Windows::iterator iter = children.begin();
+       iter != children.end();
+       ++iter) {
+    delete *iter;
+  }
   instance = NULL;
 }