Make gn check //examples/* pass

examples/sample_app/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_application.gni")
 
 mojo_native_application("sample_app") {
   sources = [
     "gles2_client_impl.cc",
     "gles2_client_impl.h",
     "sample_app.cc",
   ]
 
   deps = [
     ":spinning_cube",
     "//base",
     "//gpu/command_buffer/client:gles2_interface",
     "//mojo/public/c/system:for_shared_library",
     "//mojo/public/cpp/application:standalone",
     "//mojo/public/cpp/bindings",
+    "//mojo/public/cpp/environment",
+    "//mojo/public/cpp/system",
     "//mojo/public/cpp/utility",
     "//mojo/public/gles2:for_shared_library",
     "//mojo/services/public/interfaces/geometry",
     "//mojo/services/public/interfaces/native_viewport",
   ]
 }
 
 source_set("spinning_cube") {
   sources = [
     "spinning_cube.cc",
     "spinning_cube.h"
   ]
 
   deps = [
     "//base",
     "//mojo/public/gles2:for_shared_library",
   ]
 }