Added a timezone policy and pyauto tests for it.

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 fcdab00ecbda17fb8a4cf82b9e2c1e8cdb5e673b..1db18b7f8a476e9a6057de557a3d273c2f9931e8 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: 153
+#   For your editing convenience: highest ID currently used: 154
 #
 # Placeholders:
 #   The following placeholder strings are automatically substituted:
@@ -3100,6 +3100,22 @@
 
       If disabled or not specified, taking screenshots is allowed.'''
     },
+    {
+      'name': 'DeviceTimezone',
+      'type': 'string',
+      'schema': { 'type': 'string' },
+      'supported_on': ['chrome_os:22-'],
+      'device_only': True,
+      'features': {'dynamic_refresh': True},
+      'example_value': 'America/Los_Angeles',
+      'id': 154,
+      'caption': '''Timezone''',
+      'desc': '''Specifies the timezone to be used for the device. Users can override the specified timezone for the current session.
+      However, on logout it is set back to the specified timezone.
+
+      If this policy is not used or set to an invalid value, users can change the timezone and the change is persistent. Thus a change affects the login-screen and other users.
+      If additionally no user ever set a timezone, a default value (currently "US/Pacific") is used.''',
+    },
   ],
   'messages': {
     # Messages that are not associated to any policies.