GoBackend: Use the android VpnService to encapsulate the go backend

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

app/src/main/java/com/wireguard/android/activity/BaseActivity.java

@@ -1,11 +1,13 @@
 package com.wireguard.android.activity;
 
 import android.app.Activity;
+import android.content.Intent;
 import android.databinding.CallbackRegistry;
 import android.databinding.CallbackRegistry.NotifierCallback;
 import android.os.Bundle;
 
 import com.wireguard.android.Application;
+import com.wireguard.android.backend.GoBackend;
 import com.wireguard.android.model.Tunnel;
 import com.wireguard.android.model.TunnelManager;
 
@@ -42,8 +44,16 @@ public abstract class BaseActivity extends Activity {
             final TunnelManager tunnelManager = Application.getComponent().getTunnelManager();
             selectedTunnel = tunnelManager.getTunnels().get(savedTunnelName);
         }
+
         // The selected tunnel must be set before the superclass method recreates fragments.
         super.onCreate(savedInstanceState);
+
+        if (Application.getComponent().getBackendType() == GoBackend.class) {
+            Intent intent = GoBackend.VpnService.prepare(this);
+            if (intent != null) {
+                startActivityForResult(intent, 0);
+            }
+        }
     }
 
     @Override