Rename is_chromeos in chrome/src.

tools/perf/clear_system_cache/BUILD.gn

 # Copyright 2015 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.
 
-if (is_linux && !is_chromeos) {
+if (is_linux && !is_chromeos_ui) {
   # TODO(GYP): Figure out which of these work and are needed on other platforms.
   executable("clear_system_cache") {
     testonly = true
 
     sources = [
       "clear_system_cache_main.cc",
     ]
 
     deps = [
       "//base",
       "//base/test:test_support",
     ]
   }
 }