Offline state detection for linux, using new D-Bus library.

net/base/network_change_notifier_linux.h

 // Copyright (c) 2011 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_LINUX_H_
 #define NET_BASE_NETWORK_CHANGE_NOTIFIER_LINUX_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "net/base/network_change_notifier.h"
 
+namespace dbus {
+class Bus;
+}
+
 namespace net {
 
 class NetworkChangeNotifierLinux : public NetworkChangeNotifier {
  public:
   NetworkChangeNotifierLinux();
+  virtual ~NetworkChangeNotifierLinux();
+
+ protected:
+  // For testing.
+  explicit NetworkChangeNotifierLinux(dbus::Bus* bus);

[satorux1, 2011/10/26 17:37:09]

Function overloading is prohibited per our style guide.

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Functi...

I'd recommend to make it a static function like

NetworkChangeNotifierLinux* CreateForTesting(dbus::Bus* bus);

[adamk, 2011/10/26 18:35:52]

My reading of that section is not to prohibit operator overloading, only to
restrict it to cases where "a reader at a call site can get a good idea of what
is happening", which I think this falls under (this constructor is only called
in tests).  Here, the only options are to 1) overload the constructor or 2) make
this the only constructor, and pass in NULL in the production code (there's also
3: pass in a fully constructed dbus::Bus always, but that seems to me to leak
too much implementation detail). Which would you prefer?
This CreateForTesting() still needs to call some constructor, so it doesn't
resolve the above question.

[satorux1, 2011/10/26 18:53:15]

Let's go with 1).
You are right. For this to work, we also need to add Create(); that calls the
constructor with NULL, but it's too much work.

[adamk, 2011/10/26 19:09:34]

Actually, there's only one caller in production code, so adding a Create method
is easy enough.  Done (and removed the other constructor).  Though I don't mind
the overloading, I do hate that C++98 doesn't allow constructors to share code,
so this strikes me as a cleaner approach.

+
+  // NetworkChangeNotifier implementation.
+  // Protected for testing.
+  virtual bool IsCurrentlyOffline() const OVERRIDE;
 
  private:
   class Thread;
 
-  virtual ~NetworkChangeNotifierLinux();
-
-  // NetworkChangeNotifier:
-  virtual bool IsCurrentlyOffline() const OVERRIDE;
-
   // The thread used to listen for notifications.  This relays the notification
   // to the registered observers without posting back to the thread the object
   // was created on.
   scoped_ptr<Thread> notifier_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifierLinux);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_NETWORK_CHANGE_NOTIFIER_LINUX_H_