Makes AshTestHelper shutdown ChromeOS NetworkHandler

ash/mus/window_manager_application.cc

Index: ash/mus/window_manager_application.cc
diff --git a/ash/mus/window_manager_application.cc b/ash/mus/window_manager_application.cc
index c3dbcf58f3767b43a26762b77312395bebfe22a1..fe65aefd520c5bc61b5abd56fcf11a74bf3cc39b 100644
--- a/ash/mus/window_manager_application.cc
+++ b/ash/mus/window_manager_application.cc
@@ -99,7 +99,9 @@ void WindowManagerApplication::ShutdownComponents() {
   chromeos::CrasAudioHandler::Shutdown();
   chromeos::NetworkConnect::Shutdown();
   network_connect_delegate_.reset();
-  chromeos::NetworkHandler::Shutdown();
+  // Tests may explicitly shutdown the NetworkHandler.
+  if (chromeos::NetworkHandler::IsInitialized())
+    chromeos::NetworkHandler::Shutdown();
   device::BluetoothAdapterFactory::Shutdown();
   bluez::BluezDBusManager::Shutdown();
   chromeos::DBusThreadManager::Shutdown();