Remove non-chromeos support from src/ash BUILD.gn files

ash/common/strings/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("//tools/grit/grit_rule.gni")
 import("//tools/grit/repack.gni")
 
+assert(is_chromeos)
+
 grit("strings") {
   source = "../../ash_strings.grd"
   outputs = [
     "grit/ash_strings.h",
     "ash_strings_am.pak",
     "ash_strings_ar.pak",
     "ash_strings_bg.pak",
     "ash_strings_bn.pak",
     "ash_strings_ca.pak",
     "ash_strings_cs.pak",
@@ skipping 50 matching lines @@
 
 # Creates locale-specific pak files with strings needed for ash_unittests, etc.
 template("repack_one_locale_ash") {
   locale = invoker.locale
   output = invoker.output
 
   repack(target_name) {
     # Each input pak file should also have a deps line for completeness.
     sources = [
       "$root_gen_dir/ash/common/strings/ash_strings_${locale}.pak",
+      "$root_gen_dir/device/bluetooth/strings/bluetooth_strings_${locale}.pak",
+      "$root_gen_dir/ui/chromeos/strings/ui_chromeos_strings_${locale}.pak",
       "$root_gen_dir/ui/strings/app_locale_settings_${locale}.pak",
       "$root_gen_dir/ui/strings/ui_strings_${locale}.pak",
     ]
 
     deps = [
       "//ash/common/strings",
+      "//device/bluetooth/strings",
+      "//ui/chromeos/strings",
       "//ui/strings:app_locale_settings",
       "//ui/strings:ui_strings",
     ]
-
-    if (is_chromeos) {
-      sources += [
-        "$root_gen_dir/device/bluetooth/strings/bluetooth_strings_${locale}.pak",
-        "$root_gen_dir/ui/chromeos/strings/ui_chromeos_strings_${locale}.pak",
-      ]
-      deps += [
-        "//device/bluetooth/strings",
-        "//ui/chromeos/strings",
-      ]
-    }
   }
 }
 
 # Creates a pak file containing en-US strings for ash_unittests, etc.
 repack_one_locale_ash("ash_test_strings") {
   output = "$root_build_dir/ash_test_strings.pak"
   locale = "en-US"
 }