Add histograms and NetLog for host cache persistence

net/log/net_log_event_type_list.h

Index: net/log/net_log_event_type_list.h
diff --git a/net/log/net_log_event_type_list.h b/net/log/net_log_event_type_list.h
index eb4ac8c57c522ab79c507269a9f042b145e76da3..4570eaa5de95a95bd3b5e2569646c6d0b151709b 100644
--- a/net/log/net_log_event_type_list.h
+++ b/net/log/net_log_event_type_list.h
@@ -3208,3 +3208,22 @@ EVENT_TYPE(HTTP_SERVER_PROPERTIES_UPDATE_CACHE)
 //    "version": <The version number>,
 //  }
 EVENT_TYPE(HTTP_SERVER_PROPERTIES_UPDATE_PREFS)
+
+// -----------------------------------------------------------------------------
+// HostCachePersistenceManager related events
+// -----------------------------------------------------------------------------
+
+// The start/end of getting the persisted HostCache value and restoring it.
+// The END phase contains the following parameters:
+//  {
+//    "success": <Whether the persisted HostCache was restored successfully>,
+//  }
+EVENT_TYPE(HOST_CACHE_PREF_READ)
+
+// This event is created when the HostCachePersistenceManager writes the cache
+// contents to prefs.
+EVENT_TYPE(HOST_CACHE_PREF_WRITE)
+
+// This event is created when the HostCachePersistenceManager starts the timer
+// for writing a cache change to prefs.
+EVENT_TYPE(HOST_CACHE_PERSISTENCE_START_TIMER)