Rename is_chromeos in chrome/src.

components/gcm_driver/BUILD.gn

Index: components/gcm_driver/BUILD.gn
diff --git a/components/gcm_driver/BUILD.gn b/components/gcm_driver/BUILD.gn
index e212080083d7eecd04e518e762ebe48acb4b5e1a..35939d1b5c8d68fe60e8e6e4c470be41189b29ca 100644
--- a/components/gcm_driver/BUILD.gn
+++ b/components/gcm_driver/BUILD.gn
@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/features.gni")
+
 # GYP version: components/gcm_driver.gypi:gcm_driver
 static_library("gcm_driver") {
   sources = [
@@ -55,7 +57,7 @@ static_library("gcm_driver") {
     "//sync/protocol",
   ]
 
-  if (is_chromeos) {
+  if (use_cros_fe) {
     deps += [ "//components/timers" ]
   }