Add device policy to disallow shutdown - ash UI modifications

ash/system/tray/default_system_tray_delegate.cc

Index: ash/system/tray/default_system_tray_delegate.cc
diff --git a/ash/system/tray/default_system_tray_delegate.cc b/ash/system/tray/default_system_tray_delegate.cc
index 2d4f3856d8216a5362025de9e5c6295fbe9bab96..516d85c7e491da824335c37dcb72a306b96d1b91 100644
--- a/ash/system/tray/default_system_tray_delegate.cc
+++ b/ash/system/tray/default_system_tray_delegate.cc
@@ -151,6 +151,9 @@ void DefaultSystemTrayDelegate::ShowSupervisedUserInfo() {
 void DefaultSystemTrayDelegate::ShowUserLogin() {
 }
 
+void DefaultSystemTrayDelegate::Restart() {
+}
+
 void DefaultSystemTrayDelegate::ShutDown() {
 }
 
@@ -268,4 +271,16 @@ void DefaultSystemTrayDelegate::RemoveCustodianInfoTrayObserver(
     CustodianInfoTrayObserver* observer) {
 }
 
+void DefaultSystemTrayDelegate::AddShutdownPolicyObserver(
+    ShutdownPolicyObserver* observer) {
+}
+
+void DefaultSystemTrayDelegate::ShouldRebootOnShutdown(
+    const RebootOnShutdownCallback& callback) {
+}
+
+void DefaultSystemTrayDelegate::RemoveShutdownPolicyObserver(
+    ShutdownPolicyObserver* observer) {
+}
+
 }  // namespace ash