[net/dns] Instrument DnsConfigService to measure performance and failures.

net/dns/dns_config_service.h

 // 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.
 
 #ifndef NET_DNS_DNS_CONFIG_SERVICE_H_
 #define NET_DNS_DNS_CONFIG_SERVICE_H_
 #pragma once
 
 #include <map>
 #include <string>
@@ skipping 85 matching lines @@
   // Can be called at most once.
   void Read(const CallbackType& callback);
 
   // Registers for notifications at NetworkChangeNotifier. Will attempt to read
   // config after watch is started by NetworkChangeNotifier. Will run |callback|
   // iff config changes from last call or should be withdrawn.
   // Can be called at most once.
   virtual void Watch(const CallbackType& callback);
 
  protected:
-  friend class DnsHostsReader;
-
   // Called when the current config (except hosts) has changed.
   void InvalidateConfig();
   // Called when the current hosts have changed.
   void InvalidateHosts();
 
   // Called with new config. |config|.hosts is ignored.
   void OnConfigRead(const DnsConfig& config);
   // Called with new hosts. Rest of the config is assumed unchanged.
   void OnHostsRead(const DnsHosts& hosts);
 
@@ skipping 14 matching lines @@
 
   // True after the first valid DnsConfig is received. Temporary, used
   // to detect DNS-changer: http://crbug.com/125599
   bool checked_rogue_dns_;
   // True after On*Read, before Invalidate*. Tells if the config is complete.
   bool have_config_;
   bool have_hosts_;
   // True if receiver needs to be updated when the config becomes complete.
   bool need_update_;
   // True if the last config sent was empty (instead of |dns_config_|).
+  // Set when |timer_| expires.
   bool last_sent_empty_;
 
+  // Initialized and updated on Invalidate* call.
+  base::TimeTicks last_invalidate_config_time_;
+  base::TimeTicks last_invalidate_hosts_time_;
+  // Initialized and updated when |timer_| expires.
+  base::TimeTicks last_sent_empty_time_;
+
   // Started in Invalidate*, cleared in On*Read.
   base::OneShotTimer<DnsConfigService> timer_;
 
   DISALLOW_COPY_AND_ASSIGN(DnsConfigService);
 };
 
 }  // namespace net
 
 #endif  // NET_DNS_DNS_CONFIG_SERVICE_H_