Add ash::VPNDelegate and Chrome OS implementation

chromeos/network/network_state.h

Index: chromeos/network/network_state.h
diff --git a/chromeos/network/network_state.h b/chromeos/network/network_state.h
index db6a153678009f63d463c28d4a21ab0fa5bb9fee..ff1a5ade1f660f0e92cb12c266408d1bdb46d892 100644
--- a/chromeos/network/network_state.h
+++ b/chromeos/network/network_state.h
@@ -92,6 +92,9 @@ class CHROMEOS_EXPORT NetworkState : public ManagedState {
   const std::string& roaming() const { return roaming_; }
   const std::string& payment_url() const { return payment_url_; }
   bool cellular_out_of_credits() const { return cellular_out_of_credits_; }
+  const std::string& vpn_provider_extension_id() const {
+      return vpn_provider_extension_id_;
+  }
 
   // Returns true if |connection_state_| is a connected/connecting state.
   bool IsConnectedState() const;
@@ -180,6 +183,11 @@ class CHROMEOS_EXPORT NetworkState : public ManagedState {
   std::string payment_url_;
   bool cellular_out_of_credits_;
 
+  // VPN property. For networks using a third-party VPN provider, this will be
+  // the provider's extension ID. For networks using the built-in OpenVPN and
+  // L2TP support, this will be an empty string.
+  std::string vpn_provider_extension_id_;
+
   // TODO(pneubeck): Remove this once (Managed)NetworkConfigurationHandler
   // provides proxy configuration. crbug.com/241775
   base::DictionaryValue proxy_config_;