XXX test gn format everything

mojo/public/tools/BUILD.gn

 # Copyright 2014 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.
 
 import("//mojo/public/mojo.gni")
 
 if (use_prebuilt_mojo_shell) {
   copy("copy_mojo_shell") {
     filename = "mojo_shell"
     if (is_win) {
       filename += ".exe"
     }
-    sources = [ "prebuilt/$filename" ]
+    sources = [
+      "prebuilt/$filename",
+    ]
     outputs = [ "$root_out_dir/$filename" ]
   }
 }