Prepare //build/module_args/mojo.gni for upcoming Mojo rolls

build/module_args/mojo.gni

Index: build/module_args/mojo.gni
diff --git a/build/module_args/mojo.gni b/build/module_args/mojo.gni
index 3d21b34c94aaaf041417314683200395a77b5a40..0454f0d2e0236f551226a9169c279b8391b96352 100644
--- a/build/module_args/mojo.gni
+++ b/build/module_args/mojo.gni
@@ -2,7 +2,9 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-# To use the prebuilt shell, simply omit this variable. Note that the prebuilt
-# shell will be used only on platforms for which it is published (currently
-# Linux and Android).
-# use_prebuilt_mojo_shell = false
+# This variable should point to the parent directory of the Mojo SDK.
+mojo_sdk_root = "//third_party/mojo/src"
+
+# Chromium builds the network service from source, as it is the
+# producer of the network service.
+use_prebuilt_network_service = false