Update Chomium's build files to work w/ latest GN binaries.

build/toolchain/android/BUILD.gn

 # Copyright 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.
 
 import("//build/config/sysroot.gni")  # Imports android/config.gni.
 import("//build/toolchain/ccache.gni")
 import("//build/toolchain/clang.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/gcc_toolchain.gni")
 
 # The Android GCC toolchains share most of the same parameters, so we have this
 # wrapper around gcc_toolchain to avoid duplication of logic.
 #
 # Parameters:
 #  - android_ndk_sysroot
 #      Sysroot for this architecture.
 #  - android_ndk_lib_dir
 #      Subdirectory inside of android_ndk_sysroot where libs go.
 #  - tool_prefix
 #      Prefix to be added to the tool names.
-#  - toolchain_cpu_arch
+#  - toolchain_cpu
 #      Same as gcc_toolchain
 template("android_gcc_toolchain") {
   gcc_toolchain(target_name) {
     # Make our manually injected libs relative to the build dir.
     android_ndk_lib = rebase_path(
             invoker.android_ndk_sysroot + "/" + invoker.android_ndk_lib_dir,
             root_build_dir)
 
     libs_section_prefix = "$android_ndk_lib/crtbegin_dynamic.o"
     libs_section_postfix = "$android_ndk_lib/crtend_android.o"
@@ skipping 88 matching lines @@
   toolchain_cpu = "aarch64"
 }
 
 android_gcc_toolchain("mips64el") {
   android_ndk_sysroot = "$android_ndk_root/$mips64_android_sysroot_subdir"
   android_ndk_lib_dir = "usr/lib64"
 
   tool_prefix = "$mips64_android_toolchain_root/bin/mipsel-linux-android-"
   toolchain_cpu = "mipsel64el"
 }