Add UMA histograms for time between policy fetches

components/policy/core/common/cloud/cloud_policy_service.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/policy/core/common/cloud/cloud_policy_service.h"
 
 #include <stddef.h>
 
 #include "base/callback.h"
 #include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/time/time.h"
+#include "components/policy/core/common/cloud/cloud_policy_constants.h"
 #include "components/policy/proto/device_management_backend.pb.h"
 
 namespace em = enterprise_management;
 
 namespace policy {
 
 CloudPolicyService::CloudPolicyService(const std::string& policy_type,
                                        const std::string& settings_entity_id,
                                        CloudPolicyClient* client,
                                        CloudPolicyStore* store)
@@ skipping 87 matching lines @@
 }
 
 void CloudPolicyService::OnStoreLoaded(CloudPolicyStore* store) {
   // Update the client with state from the store.
   const em::PolicyData* policy(store_->policy());
 
   // Timestamp.
   base::Time policy_timestamp;
   if (policy && policy->has_timestamp())
     policy_timestamp = base::Time::FromJavaTime(policy->timestamp());
+
+  const base::Time& old_timestamp = client_->last_policy_timestamp();
+  if (!policy_timestamp.is_null() && !old_timestamp.is_null() &&
+      policy_timestamp != old_timestamp) {
+    base::TimeDelta age = policy_timestamp - old_timestamp;

[bartfab (slow), 2017/06/12 15:01:58]

Nit: const

[Denis Kuznetsov (DE-MUC), 2017/07/03 10:20:00]

Done.

+    if (policy_type_ == dm_protocol::kChromeUserPolicyType) {
+      UMA_HISTOGRAM_CUSTOM_COUNTS("Enterprise.PolicyUpdatePeriod.User",
+                                  age.InDays(), 1, 1000, 100);
+    } else if (policy_type_ == dm_protocol::kChromeDevicePolicyType) {
+      UMA_HISTOGRAM_CUSTOM_COUNTS("Enterprise.PolicyUpdatePeriod.Device",
+                                  age.InDays(), 1, 1000, 100);
+    }
+  }
   client_->set_last_policy_timestamp(policy_timestamp);
 
   // Public key version.
   if (policy && policy->has_public_key_version())
     client_->set_public_key_version(policy->public_key_version());
   else
     client_->clear_public_key_version();
 
   // Finally, set up registration if necessary.
   if (policy && policy->has_request_token() && policy->has_device_id() &&
@@ skipping 49 matching lines @@
 
 void CloudPolicyService::AddObserver(Observer* observer) {
   observers_.AddObserver(observer);
 }
 
 void CloudPolicyService::RemoveObserver(Observer* observer) {
   observers_.RemoveObserver(observer);
 }
 
 }  // namespace policy