Rename is_chromeos in chrome/src.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index c320c0fdac6231dcb241938db5c1a279f05f068a..19a54177c34fc2de7b920d7459b22e11ef8f5e21 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -316,14 +316,14 @@ group("both_gn_and_gyp") {
     ]
   }
 
-  if (is_chromeos) {
+  if (use_cros_fe) {
     deps += [
       "//chromeos:chromeos_unittests",
       "//ui/chromeos:ui_chromeos_unittests",
     ]
   }
 
-  if (is_chromeos || is_mac || is_win) {
+  if (use_cros_fe || is_mac || is_win) {
     deps += [
       "//rlz:rlz_id",
       "//rlz:rlz_lib",
@@ -348,19 +348,19 @@ group("both_gn_and_gyp") {
       "//sandbox/linux:sandbox_linux_jni_unittests",
     ]
 
-    if (is_chromeos || use_ash) {
+    if (use_cros_fe || use_ash) {
       deps += [ "//components/session_manager/core" ]
     }
   }
 
-  if (is_ios || is_win || (is_linux && !is_chromeos)) {
+  if (is_ios || is_win || (is_linux && !use_cros_fe)) {
     deps += [
       "//base:base_i18n_perftests",
       "//base:base_perftests",
     ]
   }
 
-  if (is_win || (is_linux && !is_chromeos)) {
+  if (is_win || (is_linux && !use_cros_fe)) {
     # TODO(GYP): Figure out which of these should (and can) build
     # for android/chromeos/mac/ios.
     deps += [
@@ -442,7 +442,7 @@ group("both_gn_and_gyp") {
     }
   }
 
-  if (is_linux && !is_chromeos) {
+  if (is_linux && !use_cros_fe) {
     deps += [
       # TODO(GYP): Figure out which of these should (and can) build
       # under which other conditions.
@@ -610,7 +610,7 @@ group("gn_only") {
     deps += [ "//components/proximity_auth:proximity_auth_unittests" ]
   }
 
-  if (is_linux && !is_chromeos) {
+  if (is_linux && !use_cros_fe) {
     # TODO(GYP): Figure out if any of these should be in gn_all
     # and figure out how cross-platform they are
     deps += [
@@ -705,7 +705,7 @@ group("gn_only") {
 
 group("gn_mojo_targets") {
   testonly = true
-  if (is_linux && !is_chromeos) {
+  if (is_linux && !use_cros_fe) {
     # TODO(GYP): Figure out if any of these should be in gn_all
     # and figure out how cross-platform they are
     deps = [