Refresh policies from DM server periodically

chrome/browser/policy/device_management_policy_cache.cc

Index: chrome/browser/policy/device_management_policy_cache.cc
diff --git a/chrome/browser/policy/device_management_policy_cache.cc b/chrome/browser/policy/device_management_policy_cache.cc
index d9ed7a64f5f13860858ce016b21c37cfeb333ee9..534794de5619237e0f4fd6ed8697d8bfcf54469b 100644
--- a/chrome/browser/policy/device_management_policy_cache.cc
+++ b/chrome/browser/policy/device_management_policy_cache.cc
@@ -105,9 +105,10 @@ void DeviceManagementPolicyCache::LoadPolicyFromFile() {
   }
 }
 
-void DeviceManagementPolicyCache::SetPolicy(
+bool DeviceManagementPolicyCache::SetPolicy(
     const em::DevicePolicyResponse& policy) {
   DictionaryValue* value = DeviceManagementPolicyCache::DecodePolicy(policy);
+  const bool new_policy_differs = !(value->Equals(policy_.get()));
   base::Time now(base::Time::Now());
   {
     AutoLock lock(lock_);
@@ -123,6 +124,7 @@ void DeviceManagementPolicyCache::SetPolicy(
       FROM_HERE,
       new PersistPolicyTask(backing_file_path_, policy_copy,
                             base::Time::NowFromSystemTime()));
+  return new_policy_differs;
 }
 
 DictionaryValue* DeviceManagementPolicyCache::GetPolicy() {