Launch nexes from mojo_shell.

mojo/nacl/config.gni

Index: mojo/nacl/config.gni
diff --git a/build/android/pylib/base/__init__.py b/mojo/nacl/config.gni
similarity index 50%
copy from build/android/pylib/base/__init__.py
copy to mojo/nacl/config.gni
index 727e987e6b621957ed56f20af1968525a9abadcf..3c40e334390231797301b5a0bd6ed1404ff7b5a8 100644
--- a/build/android/pylib/base/__init__.py
+++ b/mojo/nacl/config.gni
@@ -1,4 +1,7 @@
-# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Copyright 2015 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.
 
+declare_args() {
+  mojo_use_nacl = false
+}