Login screen and Guest mode should use device owner preference

chrome/app/policy/policy_templates.json

Index: chrome/app/policy/policy_templates.json
diff --git a/chrome/app/policy/policy_templates.json b/chrome/app/policy/policy_templates.json
index aeb4d5c9eef409dccada3f8dfa14571174aeb9ed..63f16b8ab01e42bb89504f67d2255169a2f7e24b 100644
--- a/chrome/app/policy/policy_templates.json
+++ b/chrome/app/policy/policy_templates.json
@@ -112,7 +112,7 @@
 #   persistent IDs for all fields (but not for groups!) are needed. These are
 #   specified by the 'id' keys of each policy. NEVER CHANGE EXISTING IDs,
 #   because doing so would break the deployed wire format!
-#   For your editing convenience: highest ID currently used: 234
+#   For your editing convenience: highest ID currently used: 235
 #
 # Placeholders:
 #   The following placeholder strings are automatically substituted:
@@ -4042,6 +4042,20 @@
       The format of the value follows the names of timezones in the "IANA Time Zone Database" (see "http://en.wikipedia.org/wiki/List_of_tz_database_time"). In particular, most timezones can be referred to by "continent/large_city" or "ocean/large_city".''',
     },
     {
+      'name': 'SystemUse24HourClock',
+      'type': 'main',
+      'schema': { 'type': 'boolean' },
+      'supported_on': ['chrome_os:30-'],
+      'device_only': True,
+      'features': {
+        'dynamic_refresh': True,
+      },
+      'example_value': True,
+      'id': 235,
+      'caption': '''Use 24 hour clock by default''',
+      'desc': '''Specifies the clock format be used for the device. Users can override clock format for the current session. However, on logout it is set back to the specified value.''',

[Mattias Nissler (ping if slow), 2013/08/05 18:12:13]

Please include a sentence that describes what happens if the policy is not
configured. I know it's trivial, but admins ask these questions :)

[Alexander Alekseev, 2013/08/07 14:13:36]

Done.

+    },
+    {
       'name': 'ShowLogoutButtonInTray',
       'type': 'main',
       'schema': { 'type': 'boolean' },