Fix missing GN dependencies.

chrome/browser/ui/libgtk2ui/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.
 
 assert(is_linux, "This file should only be referenced on Linux")
 
 import("//build/config/features.gni")
 
 component("libgtk2ui") {
   sources = [
@@ skipping 82 matching lines @@
     "//base/third_party/dynamic_annotations",
     "//base:i18n",
     "//build/config/linux/gtk",
     "//build/config/linux/gtk:gtkprint",
     "//chrome/app/theme:theme_resources",
     "//chrome:extra_resources",
     "//chrome:resources",
     "//chrome:strings",
     "//components/resources",
     "//content/public/browser",
+    "//mojo/environment:chromium",
     "//printing",
     "//skia",
     "//third_party/mojo/src/mojo/edk/system",
     "//ui/aura",
     "//ui/base",
     "//ui/base/ime",
     "//ui/events",
     "//ui/events:events_base",
     "//ui/gfx",
     "//ui/gfx/x",
     "//ui/native_theme",
     "//ui/resources",
     "//ui/shell_dialogs",
     "//ui/strings",
     "//ui/views",
   ]
 }