Add histograms and NetLog for host cache persistence

components/cronet/host_cache_persistence_manager.cc

Index: components/cronet/host_cache_persistence_manager.cc
diff --git a/components/cronet/host_cache_persistence_manager.cc b/components/cronet/host_cache_persistence_manager.cc
index 97e3bdca06adaee546c63c6e3681bf3c278f7b87..a804875224dafea82147b0f6da7557e1cfe18687 100644
--- a/components/cronet/host_cache_persistence_manager.cc
+++ b/components/cronet/host_cache_persistence_manager.cc
@@ -7,8 +7,10 @@
 #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 {
 
@@ -16,12 +18,16 @@ 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_);
@@ -51,8 +57,14 @@ void HostCachePersistenceManager::ReadFromDisk() {
   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() {
@@ -61,6 +73,7 @@ void HostCachePersistenceManager::ScheduleWrite() {
   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()));
@@ -69,6 +82,7 @@ void HostCachePersistenceManager::ScheduleWrite() {
 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;