mash: Convert system tray logout button to wm common types

chrome/browser/ui/ash/system_tray_delegate_chromeos.cc

Index: chrome/browser/ui/ash/system_tray_delegate_chromeos.cc
diff --git a/chrome/browser/ui/ash/system_tray_delegate_chromeos.cc b/chrome/browser/ui/ash/system_tray_delegate_chromeos.cc
index 48bf47b4e564b8cb763b92dc56251cfd1a210a99..6ebf22d1550e94e5626530b1c58f0b7d6a55faeb 100644
--- a/chrome/browser/ui/ash/system_tray_delegate_chromeos.cc
+++ b/chrome/browser/ui/ash/system_tray_delegate_chromeos.cc
@@ -257,9 +257,6 @@ void SystemTrayDelegateChromeOS::Initialize() {
   BrowserList::AddObserver(this);
 }
 
-void SystemTrayDelegateChromeOS::Shutdown() {
-}
-
 void SystemTrayDelegateChromeOS::InitializeOnAdapterReady(
     scoped_refptr<device::BluetoothAdapter> adapter) {
   bluetooth_adapter_ = adapter;