Set up a network service bootstrap.

services/network/BUILD.gn

+# 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.
+
+copy("copy_prebuilt_network_service") {
+  filename = "network_service.mojo"
+  if (is_android) {
+    sources = [
+      "prebuilt/android-arm/$filename",
+    ]
+  } else {
+    assert(is_linux)
+    sources = [
+      "prebuilt/linux-x64/$filename",
+    ]
+  }
+  outputs = [
+    "$root_out_dir/$filename",
+  ]
+}