Remove GN back-compat toolchain code for NaCl.

build/toolchain/gcc_toolchain.gni

 # 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.
 
 import("//build/config/clang/clang.gni")
 import("//build/config/nacl/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/v8_target_cpu.gni")
 import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/goma.gni")
@@ skipping 452 matching lines @@
     nm = "${toolprefix}nm"
 
     forward_variables_from(invoker, [ "strip" ])
 
     toolchain_args = {
       if (defined(invoker.toolchain_args)) {
         forward_variables_from(invoker.toolchain_args, "*")
       }
       is_clang = true
     }
-
-    # Backwards-compatible handling for toolchain definitions in the Native
-    # Client repo.
-    #
-    # TODO(brettw) bug 634446 remove this when
-    # //native_client/src/trusted/service_runtime/linux/BUILD.gn is updated to
-    # use the new-style toolchain_args.
-    if (defined(invoker.toolchain_cpu)) {
-      assert(!defined(toolchain_args.current_cpu))
-      toolchain_args.current_cpu = invoker.toolchain_cpu
-    }
-    if (defined(invoker.toolchain_os)) {
-      assert(!defined(toolchain_args.current_os))
-      toolchain_args.current_os = invoker.toolchain_os
-    }
-    if (defined(invoker.use_debug_fission)) {
-      assert(!defined(toolchain_args.use_debug_fission))
-      toolchain_args.use_debug_fission = invoker.use_debug_fission
-    }
-    if (defined(invoker.use_gold)) {
-      assert(!defined(toolchain_args.use_gold))
-      toolchain_args.use_gold = invoker.use_gold
-    }
   }
 }