Remove Chrome OS-related GN build configuration

build/secondary/tools/grit/grit_rule.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.
 
 # Instantiate grit. This will produce a script target to run grit, and a
 # static library that compiles the .cc files.
 #
 # Parameters
 #
 #   source (required)
@@ skipping 89 matching lines @@
   ]
 } else {
   grit_defines += [
     "-D",
     "_chromium",
     "-E",
     "CHROMIUM_BUILD=chromium",
   ]
 }
 
-if (is_chromeos) {
-  grit_defines += [
-    "-D",
-    "chromeos",
-    "-D",
-    "scale_factors=2x",
-  ]
-}
-
 if (is_desktop_linux) {
   grit_defines += [
     "-D",
     "desktop_linux",
   ]
 }
 
 if (use_nss_certs) {
   grit_defines += [
     "-D",
@@ skipping 201 matching lines @@
     if (defined(invoker.configs)) {
       configs += invoker.configs
     }
 
     if (defined(invoker.visibility)) {
       visibility = invoker.visibility
     }
     output_name = grit_output_name
   }
 }