Add histograms and NetLog for host cache persistence

components/cronet/host_cache_persistence_manager.cc

 // Copyright 2017 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/cronet/host_cache_persistence_manager.h"
 
 #include <memory>
 
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/values.h"
 #include "components/prefs/pref_service.h"
+#include "net/log/net_log.h"
 
 namespace cronet {
 
 HostCachePersistenceManager::HostCachePersistenceManager(
     net::HostCache* cache,
     PrefService* pref_service,
     std::string pref_name,
-    base::TimeDelta delay)
+    base::TimeDelta delay,
+    net::NetLog* net_log)
     : cache_(cache),
       pref_service_(pref_service),
       pref_name_(pref_name),
       writing_pref_(false),
       delay_(delay),
+      net_log_(net::NetLogWithSource::Make(
+          net_log,
+          net::NetLogSourceType::HOST_CACHE_PERSISTENCE_MANAGER)),
       weak_factory_(this) {
   DCHECK(cache_);
   DCHECK(pref_service_);
 
   // Get the initial value of the pref if it's already initialized.
   if (pref_service_->HasPrefPath(pref_name_))
     ReadFromDisk();
 
   registrar_.Init(pref_service_);
   registrar_.Add(pref_name_,
                  base::Bind(&HostCachePersistenceManager::ReadFromDisk,
                             weak_factory_.GetWeakPtr()));
   cache_->set_persistence_delegate(this);
 }
 
 HostCachePersistenceManager::~HostCachePersistenceManager() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 
   timer_.Stop();
   registrar_.RemoveAll();
   cache_->set_persistence_delegate(nullptr);
 }
 
 void HostCachePersistenceManager::ReadFromDisk() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 
   if (writing_pref_)
     return;
 
+  net_log_.BeginEvent(net::NetLogEventType::HOST_CACHE_PREF_READ);
   const base::ListValue* pref_value = pref_service_->GetList(pref_name_);
-  cache_->RestoreFromListValue(*pref_value);
+  bool success = cache_->RestoreFromListValue(*pref_value);
+  net_log_.EndEvent(net::NetLogEventType::HOST_CACHE_PREF_READ,
+                    net::NetLog::BoolCallback("success", success));
+
+  UMA_HISTOGRAM_BOOLEAN("DNS.HostCache.RestoreSuccess", success);
+  UMA_HISTOGRAM_COUNTS_1000("DNS.HostCache.RestoreSize", pref_value->GetSize());
 }
 
 void HostCachePersistenceManager::ScheduleWrite() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 
   if (timer_.IsRunning())
     return;
 
+  net_log_.AddEvent(net::NetLogEventType::HOST_CACHE_PERSISTENCE_START_TIMER);
   timer_.Start(FROM_HERE, delay_,
                base::Bind(&HostCachePersistenceManager::WriteToDisk,
                           weak_factory_.GetWeakPtr()));
 }
 
 void HostCachePersistenceManager::WriteToDisk() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 
+  net_log_.AddEvent(net::NetLogEventType::HOST_CACHE_PREF_WRITE);
   base::ListValue value;
   cache_->GetAsListValue(&value, false);
   writing_pref_ = true;
   pref_service_->Set(pref_name_, value);
   writing_pref_ = false;
 }
 
 }  // namespace cronet