Rename is_chromeos in chrome/src.

device/serial/BUILD.gn

Index: device/serial/BUILD.gn
diff --git a/device/serial/BUILD.gn b/device/serial/BUILD.gn
index 099b7ade2aacd13e20f4982e28d2eea3d9f7e91f..61e273e17994aed19c116397a50c7f61dcd877d7 100644
--- a/device/serial/BUILD.gn
+++ b/device/serial/BUILD.gn
@@ -2,6 +2,7 @@
 # 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")
 import("//third_party/mojo/src/mojo/public/tools/bindings/mojom.gni")
 
 # GYP version: device/serial/serial.gyp:device_serial
@@ -52,7 +53,7 @@ static_library("serial") {
   if (is_linux) {
     deps += [ "//device/udev_linux" ]
   }
-  if (is_chromeos) {
+  if (use_cros_fe) {
     deps += [ "//chromeos" ]
   }
 }