[net] Move DnsConfigService to NetworkChangeNotifier.

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_
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/non_thread_safe.h"
 #include "base/time.h"
 #include "base/timer.h"
 // Needed on shared build with MSVS2010 to avoid multiple definitions of
 // std::vector<IPEndPoint>.
 #include "net/base/address_list.h"
 #include "net/base/ip_endpoint.h"  // win requires size of IPEndPoint
-#include "net/base/network_change_notifier.h"
 #include "net/base/net_export.h"
 #include "net/dns/dns_hosts.h"
 
 namespace base {
 class Value;
 }
 
 namespace net {
 
 // Always use 1 second timeout (followed by binary exponential backoff).
@@ skipping 41 matching lines @@
   // Maximum number of attempts, see res_state.retry.
   int attempts;
   // Round robin entries in |nameservers| for subsequent requests.
   bool rotate;
   // Enable EDNS0 extensions.
   bool edns0;
 };
 
 
 // Service for reading system DNS settings, on demand or when signalled by
-// NetworkChangeNotifier.
+// internal watchers and NetworkChangeNotifier.
 class NET_EXPORT_PRIVATE DnsConfigService
-    : NON_EXPORTED_BASE(public base::NonThreadSafe),
-      public NetworkChangeNotifier::DNSObserver {
+    : NON_EXPORTED_BASE(public base::NonThreadSafe) {
  public:
-  // Callback interface for the client, called on the same thread as Read() and
-  // Watch().
+  // Callback interface for the client, called on the same thread as
+  // ReadConfig() and WatchConfig().
   typedef base::Callback<void(const DnsConfig& config)> CallbackType;
 
   // Creates the platform-specific DnsConfigService.
   static scoped_ptr<DnsConfigService> CreateSystemService();
 
   DnsConfigService();
   virtual ~DnsConfigService();
 
   // Attempts to read the configuration. Will run |callback| when succeeded.
   // Can be called at most once.
-  void Read(const CallbackType& callback);
+  void ReadConfig(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);
+  // Registers systems watchers. Will attempt to read config after watch starts,
+  // but only if watchers started successfully. Will run |callback| iff config
+  // changes from last call or has to be withdrawn. Can be called at most once.
+  // Might require MessageLoopForIO.
+  void WatchConfig(const CallbackType& callback);
 
  protected:
+  // Immediately attempts to read the current configuration.
+  virtual void ReadNow() = 0;
+  // Registers system watchers. Returns true iff succeeds.
+  virtual bool StartWatching() = 0;
+
   // 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);
 
-  // NetworkChangeNotifier::DNSObserver:
-  // Must be defined by implementations.
-  virtual void OnDNSChanged(unsigned detail) OVERRIDE = 0;
+  void set_watch_failed(bool value) { watch_failed_ = value; }
 
  private:
+  // The timer counts from the last Invalidate* until complete config is read.
   void StartTimer();
-  // Called when the timer expires.
   void OnTimeout();
-  // Called when the config becomes complete.
+  // Called when the config becomes complete. Stops the timer.
   void OnCompleteConfig();
 
   CallbackType callback_;
 
   DnsConfig dns_config_;
 
+  // True if any of the necessary watchers failed. In that case, the service
+  // will communicate changes via OnTimeout, but will only send empty DnsConfig.
+  bool watch_failed_;
   // 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_