Rename is_chromeos.

build/config/ui.gni

 # 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.
 
 # This file contains UI-related build flags (see features.gni for Chrome
 # feature-related ones). These should theoretically be moved to the ui
 # directory.
 #
 # However, today we have many "bad" dependencies on some of these flags from,
 # e.g. base, so they need to be global to match the GYP configuration. Also,
 # anything that needs a grit define must be in either this file or features.gni.
 #
 # PLEASE TRY TO AVOID ADDING FLAGS TO THIS FILE in cases where grit isn't
 # required. See the declare_args block of BUILDCONFIG.gn for advice on how
 # to set up feature flags.
 
 declare_args() {
+  # This indicates whether the chromeos interfaces and features should be
+  # made available.  Contrast with whether we are targetting the embedded
+  # OS.  That flag controls the linking, flags, filesystems, etc. we expect.
+  use_cros_ui = is_chromeos
+
   # Indicates if Ash is enabled. Ash is the Aura Shell which provides a
   # desktop-like environment for Aura. Requires use_aura = true
   use_ash = is_win || is_linux
 
   # Indicates if Ozone is enabled. Ozone is a low-level library layer for Linux
   # that does not require X11.
   use_ozone = false
 
   # Support ChromeOS touchpad gestures with ozone.
   use_evdev_gestures = false
@@ skipping 36 matching lines @@
 # Whether to use atk, the Accessibility ToolKit library
 use_atk = is_desktop_linux && use_x11
 
 use_ozone_evdev = use_ozone
 
 use_clipboard_aurax11 = is_linux && use_aura && use_x11
 
 enable_hidpi = is_mac || is_win || is_linux
 
 enable_topchrome_md = is_chromeos || is_win || is_linux
+
+if (is_chromeos_os) {
+  assert(use_cros_ui, "ChromeOS targetting requires ChromeOS UI")
+}
+
+assert(use_cros_ui == is_chromeos,
+       "is_chromeos and use_cros_ui are expected to be aliases, " +
+           "old and new, respectively")