Added a timezone policy and pyauto tests for it.

chrome/browser/chromeos/settings/cros_settings_names.cc

Index: chrome/browser/chromeos/settings/cros_settings_names.cc
diff --git a/chrome/browser/chromeos/settings/cros_settings_names.cc b/chrome/browser/chromeos/settings/cros_settings_names.cc
index 0cb3aad2ca76871d747f49eb6e861af362300e0e..38cf3c966cf923d3e1aabf184f117acca1d027ba 100644
--- a/chrome/browser/chromeos/settings/cros_settings_names.cc
+++ b/chrome/browser/chromeos/settings/cros_settings_names.cc
@@ -23,7 +23,12 @@ const char kSettingProxyEverywhere[] = "cros.proxy.everywhere";
 // All cros.signed.* settings are stored in SignedSettings.
 const char kSignedDataRoamingEnabled[] = "cros.signed.data_roaming_enabled";
 
+// The first constant refers to the user setting editable in the UI.  The second
+// refers to the timezone policy. These are currently separated because the
+// policy stack for device settings does not support the required behavior (see
+// the description in policy_templates.json).
 const char kSystemTimezone[] = "cros.system.timezone";
+const char kSystemTimezonePolicy[] = "cros.system.timezone_policy";
 
 const char kDeviceOwner[] = "cros.device.owner";