chromeos: Refactor D-Bus client creation for ash and browser processes

chromeos/dbus/dbus_client.h

 // Copyright 2013 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 CHROMEOS_DBUS_DBUS_CLIENT_H_
 #define CHROMEOS_DBUS_DBUS_CLIENT_H_
 
 #include "base/macros.h"
 
 namespace dbus {
 class Bus;
 }  // namespace dbus
 
 namespace chromeos {
 
 // Interface for all DBus clients handled by DBusThreadManager. It restricts
 // access to the Init function to DBusThreadManager only to prevent
 // incorrect calls. Stub clients may lift that restriction however.
 class DBusClient {
  protected:
   virtual ~DBusClient() {}
 
   // This function is called by DBusThreadManager. Only in unit tests, which
   // don't use DBusThreadManager, this function can be called through Stub
   // implementations (they change Init's member visibility to public).
   virtual void Init(dbus::Bus* bus) = 0;
 
  private:
-  friend class DBusThreadManager;
+  friend class DBusClientsAsh;
+  friend class DBusClientsBrowser;
+  friend class DBusClientsCommon;
 
   DISALLOW_ASSIGN(DBusClient);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DBUS_DBUS_CLIENT_H_