Add device policy to disallow shutdown

chrome/browser/chromeos/policy/proto/chrome_device_policy.proto

Index: chrome/browser/chromeos/policy/proto/chrome_device_policy.proto
diff --git a/chrome/browser/chromeos/policy/proto/chrome_device_policy.proto b/chrome/browser/chromeos/policy/proto/chrome_device_policy.proto
index f5c1a4cd9b669076f92b61343f8bb82b52c28458..9c2574a637f4c651cbb2b116d2b050bad6f2b776 100644
--- a/chrome/browser/chromeos/policy/proto/chrome_device_policy.proto
+++ b/chrome/browser/chromeos/policy/proto/chrome_device_policy.proto
@@ -583,6 +583,13 @@ message SAMLSettingsProto {
   optional bool transfer_saml_cookies = 1;
 }
 
+message ShutdownAllowedProto {
+  // Determines if the device may be shut down. This policy controls shut down
+  // via the UI only. If shutdown is forbidden, UI elements trigger a device
+  // reboot instead of a power off.
+  optional bool shutdown_allowed = 1 [default = true];
+}
+
 message ChromeDeviceSettingsProto {
   optional DevicePolicyRefreshRateProto device_policy_refresh_rate = 1;
   optional UserWhitelistProto user_whitelist = 2;
@@ -617,4 +624,5 @@ message ChromeDeviceSettingsProto {
   optional AutoCleanupSettigsProto auto_clean_up_settings = 31;
   optional SystemSettingsProto system_settings = 32;
   optional SAMLSettingsProto saml_settings = 33;
+  optional ShutdownAllowedProto shutdown_allowed = 34;
 }