Aura Shell singleton needs to be destroyed prior to the Aura Desktop

ui/aura_shell/examples/aura_shell_main.cc

Index: ui/aura_shell/examples/aura_shell_main.cc
diff --git a/ui/aura_shell/examples/aura_shell_main.cc b/ui/aura_shell/examples/aura_shell_main.cc
index 8a8ee4c3861e01d99b5afd887cf85b17e7df1d3a..d0429c97c1c1e3bf716bf26329d8864fb9e601ac 100644
--- a/ui/aura_shell/examples/aura_shell_main.cc
+++ b/ui/aura_shell/examples/aura_shell_main.cc
@@ -123,6 +123,8 @@ int main(int argc, char** argv) {
 
   aura::RootWindow::GetInstance()->Run();
 
+  aura_shell::Shell::DeleteInstance();
+
   aura::RootWindow::DeleteInstance();
 
   ui::CompositorTestSupport::Terminate();