Rename is_chromeos in chrome/src.

chrome/common/BUILD.gn

Index: chrome/common/BUILD.gn
diff --git a/chrome/common/BUILD.gn b/chrome/common/BUILD.gn
index 44e5aa218d5597bdc5b1f4d18feb15a95cdd1700..2de47c39b03ecf46ba2ef8df744cba412b668f72 100644
--- a/chrome/common/BUILD.gn
+++ b/chrome/common/BUILD.gn
@@ -125,7 +125,7 @@ static_library("common") {
       "//extensions/strings",
       "//media/cast:net",
     ]
-    if (is_chromeos) {
+    if (use_cros_fe) {
       sources +=
           rebase_path(gypi_values.chrome_common_extensions_chromeos_sources,
                       ".",
@@ -138,7 +138,7 @@ static_library("common") {
         rebase_path(gypi_values.chrome_common_win_mac_sources, ".", "//chrome")
     deps += [ "//breakpad:client" ]
   }
-  if (is_win || is_mac || is_chromeos) {
+  if (is_win || is_mac || use_cros_fe) {
     if (use_openssl) {
       sources += rebase_path(
               gypi_values.chrome_common_networking_private_sources_openssl,
@@ -204,7 +204,7 @@ static_library("common") {
         rebase_path(gypi_values.chrome_common_importer_sources, ".", "//chrome")
   }
 
-  if (is_chromeos) {
+  if (use_cros_fe) {
     sources -= [ "channel_info_posix.cc" ]
   }