Move the cros_* GN args to a .gni file and add a bootstrap cros toolchain.

build/toolchain/cros_toolchain.gni

-# Copyright 2014 The Chromium Authors. All rights reserved.
+# Copyright 2016 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.
 
-import("//build/toolchain/gcc_toolchain.gni")
-
 # CrOS builds must cross-compile on a Linux host for the actual CrOS
 # device target. There are many different CrOS devices so the build
 # system provides configuration variables that permit a CrOS build to
 # control the cross-compilation tool chain. However, requiring such
 # fine-grain specification is tedious for build-bots and developers.
 # Consequently, the CrOS build system defaults to a convenience
 # compilation mode where the compilation host is also the build target.
 #
 # Chrome can be compiled in this way with the gn variable:
 #
@@ skipping 52 matching lines @@
   cros_v8_snapshot_cxx = "g++"
   cros_v8_snapshot_ld = ""
   cros_v8_snapshot_nm = ""
   cros_v8_snapshot_readelf = ""
   cros_v8_snapshot_extra_cflags = ""
   cros_v8_snapshot_extra_cppflags = ""
   cros_v8_snapshot_extra_cxxflags = ""
   cros_v8_snapshot_extra_ldflags = ""
   cros_v8_snapshot_is_clang = false
 }
-
-# TODO(dpranke): Delete this after we get rid of the reference to
-# build/toolchain/cros:clang_target in BUILDCONFIG.gn
-clang_toolchain("clang_target") {
-  toolchain_cpu = target_cpu
-  toolchain_os = "linux"
-}
-
-gcc_toolchain("target") {
-  # These are args for the template.
-  ar = cros_target_ar
-  cc = cros_target_cc
-  cxx = cros_target_cxx
-  ld = cxx
-  if (cros_target_ld != "") {
-    ld = cros_target_ld
-  }
-  if (cros_target_nm != "") {
-    nm = cros_target_nm
-  }
-  if (cros_target_readelf != "") {
-    readelf = cros_target_readelf
-  }
-  extra_cflags = cros_target_extra_cflags
-  extra_cppflags = cros_target_extra_cppflags
-  extra_cxxflags = cros_target_extra_cxxflags
-  extra_ldflags = cros_target_extra_ldflags
-
-  # These are passed through as toolchain_args.
-  cc_wrapper = ""
-  is_clang = is_clang
-  toolchain_cpu = target_cpu
-  toolchain_os = "linux"
-}
-
-gcc_toolchain("host") {
-  # These are args for the template.
-  ar = cros_host_ar
-  cc = cros_host_cc
-  cxx = cros_host_cxx
-  ld = cxx
-  if (cros_host_ld != "") {
-    ld = cros_host_ld
-  }
-  if (cros_host_nm != "") {
-    nm = cros_host_nm
-  }
-  if (cros_host_readelf != "") {
-    readelf = cros_host_readelf
-  }
-  extra_cflags = cros_host_extra_cflags
-  extra_cppflags = cros_host_extra_cppflags
-  extra_cxxflags = cros_host_extra_cxxflags
-  extra_ldflags = cros_host_extra_ldflags
-
-  # These are passed through as toolchain_args.
-  cc_wrapper = ""
-  is_clang = cros_host_is_clang
-  toolchain_cpu = host_cpu
-  toolchain_os = "linux"
-  use_sysroot = false
-}
-
-gcc_toolchain("v8_snapshot") {
-  # These are args for the template.
-  ar = cros_v8_snapshot_ar
-  cc = cros_v8_snapshot_cc
-  cxx = cros_v8_snapshot_cxx
-  ld = cxx
-  if (cros_v8_snapshot_ld != "") {
-    ld = cros_v8_snapshot_ld
-  }
-  if (cros_v8_snapshot_nm != "") {
-    nm = cros_v8_snapshot_nm
-  }
-  if (cros_v8_snapshot_readelf != "") {
-    readelf = cros_v8_snapshot_readelf
-  }
-  extra_cflags = cros_v8_snapshot_extra_cflags
-  extra_cppflags = cros_v8_snapshot_extra_cppflags
-  extra_cxxflags = cros_v8_snapshot_extra_cxxflags
-  extra_ldflags = cros_v8_snapshot_extra_ldflags
-
-  # These are passed through as toolchain_args.
-  cc_wrapper = ""
-  is_clang = cros_v8_snapshot_is_clang
-  if (target_cpu == "x86" || target_cpu == "arm" || target_cpu == "mipsel") {
-    toolchain_cpu = "x86"
-  } else {
-    toolchain_cpu = "x64"
-  }
-  toolchain_os = "linux"
-  use_sysroot = false
-}