Add ash::VPNDelegate and Chrome OS implementation

ash/system/tray/system_tray_delegate.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 ASH_SYSTEM_TRAY_SYSTEM_TRAY_DELEGATE_H_
 #define ASH_SYSTEM_TRAY_SYSTEM_TRAY_DELEGATE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 81 matching lines @@
   ~UpdateInfo();
 
   UpdateSeverity severity;
   bool update_required;
   bool factory_reset_required;
 };
 
 using IMEInfoList = std::vector<IMEInfo>;
 
 class NetworkingConfigDelegate;
+class VPNDelegate;
 
 using RebootOnShutdownCallback = base::Callback<void(bool)>;
 
 namespace tray {
 class UserAccountsDelegate;
 }  // namespace tray
 
 // SystemTrayDelegate is intended for delegating tasks in the System Tray to the
 // application (e.g. Chrome). These tasks should be limited to application
 // (browser) specific tasks. For non application specific tasks, where possible,
@@ skipping 213 matching lines @@
   // the |DeviceRebootOnShutdown| policy changes. If this policy is set to
   // true, a device cannot be shut down anymore but only rebooted.
   virtual void AddShutdownPolicyObserver(ShutdownPolicyObserver* observer);
 
   virtual void RemoveShutdownPolicyObserver(ShutdownPolicyObserver* observer);
 
   // Determines whether the device is automatically rebooted when shut down as
   // specified by the device policy |DeviceRebootOnShutdown|. This function
   // asynchronously calls |callback| once a trusted policy becomes available.
   virtual void ShouldRebootOnShutdown(const RebootOnShutdownCallback& callback);
+
+  // Returns VPNDelegate. May return nullptr.
+  virtual VPNDelegate* GetVPNDelegate() const;
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_DELEGATE_H_