Move tray code from ui/chromeos/network/

ui/chromeos/material_design_icon_controller.cc

-// Copyright 2016 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.
-
-#include "ui/chromeos/material_design_icon_controller.h"
-
-namespace ui {
-namespace md_icon_controller {
-
-namespace {
-bool use_md_network_icons = false;
-}  // namespace
-
-void SetUseMaterialDesignNetworkIcons(bool use) {
-  use_md_network_icons = use;
-}
-
-bool UseMaterialDesignNetworkIcons() {
-  return use_md_network_icons;
-}
-
-}  // namespace md_icon_controller
-}  // namespace ui