Adding platform support check for NetworkObserver

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 <vector>
 
 #include "base/basictypes.h"
@@ skipping 343 matching lines @@
   // called back with notifications.  This is safe to call if Create() has not
   // been called (as long as it doesn't race the Create() call on another
   // thread), in which case it will simply do nothing.
   static void AddIPAddressObserver(IPAddressObserver* observer);
   static void AddConnectionTypeObserver(ConnectionTypeObserver* observer);
   static void AddDNSObserver(DNSObserver* observer);
   static void AddNetworkChangeObserver(NetworkChangeObserver* observer);
   static void AddMaxBandwidthObserver(MaxBandwidthObserver* observer);
   static void AddNetworkObserver(NetworkObserver* observer);
 
+  // Returns true if platform supports notifications required for observer.
+  static bool IsNetworkObserverSupported();
+
   // Unregisters |observer| from receiving notifications.  This must be called
   // on the same thread on which AddObserver() was called.  Like AddObserver(),
   // this is safe to call if Create() has not been called (as long as it doesn't
   // race the Create() call on another thread), in which case it will simply do
   // nothing.  Technically, it's also safe to call after the notifier object has
   // been destroyed, if the call doesn't race the notifier's destruction, but
   // 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);
@@ skipping 174 matching lines @@
 
   // Set true to disable non-test notifications (to prevent flakes in tests).
   static bool test_notifications_only_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifier);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_NETWORK_CHANGE_NOTIFIER_H_