Added a timezone policy and pyauto tests for it.

chrome/browser/policy/device_policy_cache.cc

Index: chrome/browser/policy/device_policy_cache.cc
diff --git a/chrome/browser/policy/device_policy_cache.cc b/chrome/browser/policy/device_policy_cache.cc
index 1cf962dabc9e721384745c1f1beec4d398179712..da632e3c9e12cd6d6e17867f4aa6dd44f46e8025 100644
--- a/chrome/browser/policy/device_policy_cache.cc
+++ b/chrome/browser/policy/device_policy_cache.cc
@@ -722,6 +722,16 @@ void DevicePolicyCache::DecodeGenericPolicies(
                     urls);
     }
   }
+
+  if (policy.has_system_timezone()) {
+    if (policy.system_timezone().has_timezone()) {
+      policies->Set(key::kDeviceTimezone,
+                    POLICY_LEVEL_MANDATORY,
+                    POLICY_SCOPE_MACHINE,
+                    Value::CreateStringValue(
+                        policy.system_timezone().timezone()));
+    }
+  }
 }
 
 }  // namespace policy