Add histograms to NetworkChangeNotifier to identify ways to improve interface

net/base/network_change_notifier.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_BASE_NETWORK_CHANGE_NOTIFIER_H_
 #define NET_BASE_NETWORK_CHANGE_NOTIFIER_H_
 
 #include "base/basictypes.h"
 #include "base/observer_list_threadsafe.h"
 #include "base/synchronization/lock.h"
 #include "net/base/net_export.h"
 
+class GURL;
+
 namespace net {
 
+class HistogramWatcher;
 class NetworkChangeNotifierFactory;
 
 namespace internal {
 class DnsConfigWatcher;
 
 #if defined(OS_LINUX)
 class AddressTrackerLinux;
 #endif
 }
 
@@ skipping 145 matching lines @@
   // there's no reason to use the API in this risky way, so don't do it.
   static void RemoveIPAddressObserver(IPAddressObserver* observer);
   static void RemoveConnectionTypeObserver(ConnectionTypeObserver* observer);
   static void RemoveDNSObserver(DNSObserver* observer);
 
   // Allow unit tests to trigger notifications.
   static void NotifyObserversOfIPAddressChangeForTests() {
     NotifyObserversOfIPAddressChange();
   }
 
+  // Let the NetworkChangeNotifier know we received some data.
+  // This is used strictly for producing histogram data about the accuracy of
+  // the NetworkChangenotifier's online detection.
+  static void NotifyDataReceived(const GURL& source);
+
+  // Register the Observer callbacks for producing histogram data.  This
+  // should be called from the network thread to avoid race conditions.
+  static void InitHistogramWatcher();
+
  protected:
   friend class internal::DnsConfigWatcher;
 
   NetworkChangeNotifier();
 
 #if defined(OS_LINUX)
   // Returns the AddressTrackerLinux if present.
   virtual const internal::AddressTrackerLinux*
       GetAddressTrackerInternal() const;
 #endif
@@ skipping 33 matching lines @@
   const scoped_refptr<ObserverListThreadSafe<DNSObserver> >
       resolver_state_observer_list_;
 
   // True iff DNS watchers are operational.
   // Otherwise, OnDNSChanged might not be issued for future changes.
   // TODO(szym): This is a temporary interface, consider restarting them.
   //             http://crbug.com/116139
   base::Lock watching_dns_lock_;
   bool watching_dns_;
 
+  // A little-piggy-back observer that simply logs UMA histogram data.
+  scoped_ptr<HistogramWatcher> histogram_watcher_;
+
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifier);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_NETWORK_CHANGE_NOTIFIER_H_