Reland: chromeos: Convert ash VPNDelegate interface to mojo

ash/common/system/tray/system_tray_delegate.h

Index: ash/common/system/tray/system_tray_delegate.h
diff --git a/ash/common/system/tray/system_tray_delegate.h b/ash/common/system/tray/system_tray_delegate.h
index e1f9c249c93d05db1d05087fa5b3f4121f1306d4..61cebca539b3451789b4cc13f07cd8f3dfd023ce 100644
--- a/ash/common/system/tray/system_tray_delegate.h
+++ b/ash/common/system/tray/system_tray_delegate.h
@@ -73,14 +73,13 @@ struct ASH_EXPORT UpdateInfo {
 
 class CastConfigDelegate;
 class NetworkingConfigDelegate;
-class VPNDelegate;
 
 // 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,
 // components/, chromeos/, device/, etc., code should be used directly. If more
 // than one related method is being added, consider adding an additional
-// specific delegate (e.g. VPNDelegate).
+// specific delegate (e.g. CastConfigDelegate).
 //
 // These methods should all have trivial default implementations for platforms
 // that do not implement the method (e.g. return false or nullptr). This
@@ -219,9 +218,6 @@ class ASH_EXPORT SystemTrayDelegate {
   virtual void RemoveCustodianInfoTrayObserver(
       CustodianInfoTrayObserver* observer);
 
-  // Returns VPNDelegate. May return nullptr.
-  virtual VPNDelegate* GetVPNDelegate() const;
-
   // Creates a system tray item for display rotation lock.
   // TODO(jamescook): Remove this when mus has support for display management
   // and we have a DisplayManager equivalent. See http://crbug.com/548429