Remove Chrome OS-related GN build configuration

build/config/BUILDCONFIG.gn

 # Copyright (c) 2013 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 (target_os == "") {
   target_os = host_os
 }
 
 if (target_cpu == "") {
   if (target_os == "android") {
@@ skipping 76 matching lines @@
   #   -1 means auto-set (off in release, regular in debug).
   symbol_level = -1
 
   # Component build.
   is_component_build = false
 
   # Debug build.
   is_debug = true
 
   # Whether we're a traditional desktop unix.
-  is_desktop_linux = current_os == "linux" && current_os != "chromeos"
+  is_desktop_linux = current_os == "linux"
 
   # Set to true when compiling with the Clang compiler. Typically this is used
   # to configure warnings.
-  is_clang = current_os == "mac" || current_os == "ios" ||
-             current_os == "linux" || current_os == "chromeos"
+  is_clang = current_os == "mac" || current_os == "ios" || current_os == "linux"
 
   # By default, assume a non-PNaCl toolchain.
   is_pnacl = false
 
   # Selects the desired build flavor. Official builds get additional
   # processing to prepare for release. Normally you will want to develop and
   # test with this flag off.
   # TODO(brettw) move to chrome_build.gni when DEPS are updated.
   is_official_build = false
 
   # Select the desired branding flavor. False means normal Chromium branding,
   # true means official Google Chrome branding (requires extra Google-internal
   # resources).
   # TODO(brettw) move to chrome_build.gni when DEPS are updated.
   is_chrome_branded = false
 
   # Compile for Address Sanitizer to find memory bugs.
   is_asan = false
 
   # Compile for Leak Sanitizer to find leaks.
   is_lsan = false
 
   # Compile for Memory Sanitizer to find uninitialized reads.
   is_msan = false
 
   # Compile for Thread Sanitizer to find threading bugs.
   is_tsan = false
 
-  if (current_os == "chromeos") {
-    # Allows the target toolchain to be injected as arguments. This is needed
-    # to support the CrOS build system which supports per-build-configuration
-    # toolchains.
-    cros_use_custom_toolchain = false
-  }
-
   # DON'T ADD MORE FLAGS HERE. Read the comment above.
 }
 
 # =============================================================================
 # OS DEFINITIONS
 # =============================================================================
 #
 # We set these various is_FOO booleans for convenience in writing OS-based
 # conditions.
 #
-# - is_android, is_chromeos, is_ios, and is_win should be obvious.
+# - is_android, is_ios, and is_win should be obvious.
 # - is_mac is set only for desktop Mac. It is not set on iOS.
 # - is_posix is true for mac and any Unix-like system (basically everything
 #   except Windows).
-# - is_linux is true for desktop Linux and ChromeOS, but not Android (which is
+# - is_linux is true for desktop Linux, but not Android (which is
 #   generally too different despite being based on the Linux kernel).
 #
 # Do not add more is_* variants here for random lesser-used Unix systems like
 # aix or one of the BSDs. If you need to check these, just check the
 # current_os value directly.
 
 if (current_os == "mac") {
   is_android = false
   is_chromeos = false
   is_fnl = false
   is_ios = false
   is_linux = false
   is_mac = true
   is_nacl = false
   is_posix = true
   is_win = false
 } else if (current_os == "android") {
   is_android = true
   is_chromeos = false
   is_fnl = false
   is_ios = false
   is_linux = false
   is_mac = false
   is_nacl = false
   is_posix = true
   is_win = false
-} else if (current_os == "chromeos") {
-  is_android = false
-  is_chromeos = true
-  is_fnl = false
-  is_ios = false
-  is_linux = true
-  is_mac = false
-  is_nacl = false
-  is_posix = true
-  is_win = false
 } else if (current_os == "nacl") {
   # current_os == "nacl" will be passed by the nacl toolchain definition.
   # It is not set by default or on the command line. We treat is as a
   # Posix variant.
   is_android = false
   is_chromeos = false
   is_fnl = false
   is_ios = false
   is_linux = false
   is_mac = false
@@ skipping 351 matching lines @@
   }
   set_default_toolchain("//build/toolchain/android:$current_cpu")
 } else if (is_linux) {
   if (is_clang) {
     host_toolchain = "//build/toolchain/linux:clang_$host_cpu"
     set_default_toolchain("//build/toolchain/linux:clang_$current_cpu")
   } else {
     host_toolchain = "//build/toolchain/linux:$host_cpu"
     set_default_toolchain("//build/toolchain/linux:$current_cpu")
   }
-  if (is_chromeos && cros_use_custom_toolchain) {
-    set_default_toolchain("//build/toolchain/cros:target")
-  }
   if (is_fnl) {
     set_default_toolchain("//build/toolchain/fnl:target")
   }
 } else if (is_mac) {
   host_toolchain = "//build/toolchain/mac:clang_x64"
   set_default_toolchain(host_toolchain)
 } else if (is_ios) {
   host_toolchain = "//build/toolchain/mac:clang_x64"
   set_default_toolchain("//build/toolchain/mac:clang_$current_cpu")
 } else if (is_nacl) {
@@ skipping 198 matching lines @@
       }
       if (defined(invoker.testonly)) {
         testonly = invoker.testonly
       }
       if (defined(invoker.visibility)) {
         visibility = invoker.visibility
       }
     }
   }
 }