Start calculating new combined NetworkChangeNotifier signal

net/base/network_change_notifier.h

Index: net/base/network_change_notifier.h
diff --git a/net/base/network_change_notifier.h b/net/base/network_change_notifier.h
index 84e399ee6c28162d53fc49695e1c51109b09a5a8..1884c8eb061d690eafe1a55a8f7bbad165cf029f 100644
--- a/net/base/network_change_notifier.h
+++ b/net/base/network_change_notifier.h
@@ -86,6 +86,43 @@ class NET_EXPORT NetworkChangeNotifier {
     DISALLOW_COPY_AND_ASSIGN(DNSObserver);
   };
 
+  class NET_EXPORT NetworkChangeObserver {
+   public:
+    // OnNetworkChanged will be called when a change occurs to the host
+    // computer's hardware or software that affects the route network packets
+    // take to any network server. Some examples:
+    //   1. A network connection becoming available or going away. For example
+    //      plugging or unplugging an Ethernet cable, WiFi or cellular modem
+    //      connecting or disconnecting from a network, or a VPN tunnel being
+    //      established or taken down.
+    //   2. An active network connection's IP address changes.
+    //   3. A change to the local IP routing tables.
+    // The signal shall only be produced when the change is complete.  For
+    // example if a new network connection has become available, only give the
+    // signal once we think the O/S has finished establishing the connection
+    // (i.e. DHCP is done) to the point where the new connection is usable.
+    // The signal shall not be produced spuriously as it will be triggering some
+    // expensive operations, like socket pools closing all connections and
+    // sockets and then re-establishing them.
+    // |type| indicates the type of the active primary network connection after
+    // the change.  Observers performing "constructive" activities like trying
+    // to establish a connection to a server should only do so when
+    // |type != CONNECTION_NONE|.  Observers performing "destructive" activities
+    // like resetting already established server connections should only do so
+    // when |type == CONNECTION_NONE|.  OnNetworkChanged will be called with
+    // CONNECTION_NONE immediately prior to being called with an online state;
+    // this is done to make sure that destructive actions take place prior to
+    // constructive actions.
+    virtual void OnNetworkChanged(ConnectionType type) = 0;
+
+   protected:
+    NetworkChangeObserver() {}
+    virtual ~NetworkChangeObserver() {}
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(NetworkChangeObserver);
+  };
+
   virtual ~NetworkChangeNotifier();
 
   // See the description of NetworkChangeNotifier::GetConnectionType().
@@ -155,6 +192,7 @@ class NET_EXPORT NetworkChangeNotifier {
   static void AddIPAddressObserver(IPAddressObserver* observer);
   static void AddConnectionTypeObserver(ConnectionTypeObserver* observer);
   static void AddDNSObserver(DNSObserver* observer);
+  static void AddNetworkChangeObserver(NetworkChangeObserver* observer);
 
   // Unregisters |observer| from receiving notifications.  This must be called
   // on the same thread on which AddObserver() was called.  Like AddObserver(),
@@ -166,6 +204,7 @@ class NET_EXPORT NetworkChangeNotifier {
   static void RemoveIPAddressObserver(IPAddressObserver* observer);
   static void RemoveConnectionTypeObserver(ConnectionTypeObserver* observer);
   static void RemoveDNSObserver(DNSObserver* observer);
+  static void RemoveNetworkChangeObserver(NetworkChangeObserver* observer);
 
   // Allow unit tests to trigger notifications.
   static void NotifyObserversOfIPAddressChangeForTests() {
@@ -185,7 +224,14 @@ class NET_EXPORT NetworkChangeNotifier {
   static void InitHistogramWatcher();
 
  protected:
-  NetworkChangeNotifier();
+  // Delay arguments control how many milliseconds to delay notifications
+  // so as to combine duplicates.  They should be tuned for the particular
+  // child class implementation.  See NetworkChangeCalculator() for more
+  // details.
+  NetworkChangeNotifier(uint32 ip_address_offline_delay_ms,
+                        uint32 ip_address_online_delay_ms,
+                        uint32 connection_type_offline_delay_ms,
+                        uint32 connection_type_online_delay_ms);

[szym, 2012/11/25 07:37:37]

They should be TimeDelta.

I suggest using four independent setters. This would improve readability, and
allow reasonable default (i.e., 0). If you insist on grouping them together, I
suggest one setter for
struct NetworkChangeCalculatorParams {
  TimeDelta ip_address_offline_delay;
  // ...
};

If this has to be passed at construction time, then you can add static
NetworkChangeCalculatorParams NetworkChangeCalculatorParams::Defaults() (if you
want to keep the struct POD) or a default constructor (if not).

This would also allow you to create constructor functions (in anonymous
namespace) where the constants are well-named and readable.

 
 #if defined(OS_LINUX)
   // Returns the AddressTrackerLinux if present.
@@ -200,6 +246,7 @@ class NET_EXPORT NetworkChangeNotifier {
   static void NotifyObserversOfIPAddressChange();
   static void NotifyObserversOfConnectionTypeChange();
   static void NotifyObserversOfDNSChange();
+  static void NotifyObserversOfNetworkChange(ConnectionType type);
 
   // Stores |config| in NetworkState and notifies observers.
   static void SetDnsConfig(const DnsConfig& config);
@@ -211,6 +258,7 @@ class NET_EXPORT NetworkChangeNotifier {
   friend class NetworkChangeNotifierWinTest;
 
   class NetworkState;
+  class NetworkChangeCalculator;
 
   // Allows a second NetworkChangeNotifier to be created for unit testing, so
   // the test suite can create a MockNetworkChangeNotifier, but platform
@@ -235,6 +283,8 @@ class NET_EXPORT NetworkChangeNotifier {
       connection_type_observer_list_;
   const scoped_refptr<ObserverListThreadSafe<DNSObserver> >
       resolver_state_observer_list_;
+  const scoped_refptr<ObserverListThreadSafe<NetworkChangeObserver> >
+      network_change_observer_list_;
 
   // The current network state. Hosts DnsConfig, exposed via GetDnsConfig.
   scoped_ptr<NetworkState> network_state_;
@@ -242,6 +292,9 @@ class NET_EXPORT NetworkChangeNotifier {
   // A little-piggy-back observer that simply logs UMA histogram data.
   scoped_ptr<HistogramWatcher> histogram_watcher_;
 
+  // Computes NetworkChange signal from IPAddress and ConnectionType signals.
+  scoped_ptr<NetworkChangeCalculator> network_change_calculator_;
+
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifier);
 };