VPN: introduce VpnService as the base class for user space VPN.

Change-Id: I4793a6eb51b33f669fc6d39e1a16cf5eb9e3d851
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index 19a25cc..d921fe6 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -1119,6 +1119,14 @@
         android:description="@string/permdesc_bindTextService"
         android:protectionLevel="signature" />
 
+    <!-- Must be required by an {@link android.net.VpnService},
+         to ensure that only the system can bind to it.
+         @hide -->
+    <permission android:name="android.permission.BIND_VPN_SERVICE"
+        android:label="@string/permlab_bindVpnService"
+        android:description="@string/permdesc_bindVpnService"
+        android:protectionLevel="signature" />
+
     <!-- Must be required by a {@link android.service.wallpaper.WallpaperService},
          to ensure that only the system can bind to it. -->
     <permission android:name="android.permission.BIND_WALLPAPER"