Enables GN build on windows

build/toolchain/win/BUILD.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.
 
 declare_args() {
   # Path to the directory containing the VC binaries for the right
   # combination of host and target architectures. Currently only the
   # 64-bit host toolchain is supported, with either 32-bit or 64-bit targets.
   # If vc_bin_dir is not specified on the command line (and it normally
   # isn't), we will dynamically determine the right value to use at runtime.
   vc_bin_dir = ""
 }
 
 import("//build/config/win/visual_studio_version.gni")
 import("//build/toolchain/goma.gni")
 
 # Should only be running on Windows.
 assert(is_win)
 
 # Setup the Visual Studio state.
 #
 # Its arguments are the VS path and the compiler wrapper tool. It will write
 # "environment.x86" and "environment.x64" to the build directory and return a
 # list to us.
 gyp_win_tool_path =
-    rebase_path("//tools/gyp/pylib/gyp/win_tool.py", root_build_dir)
+    rebase_path("//third_party/gyp/pylib/gyp/win_tool.py", root_build_dir)
 
 toolchain_data = exec_script("setup_toolchain.py",
                              [
                                visual_studio_path,
                                gyp_win_tool_path,
                                windows_sdk_path,
                                visual_studio_runtime_dirs,
                                current_cpu,
                              ],
                              "scope")
 
 if (vc_bin_dir == "") {
   vc_bin_dir = toolchain_data.vc_bin_dir
 }
 
 if (use_goma) {
   goma_prefix = "$goma_dir/gomacc.exe "
 } else {
   goma_prefix = ""
 }
 
-# This value will be inherited in the toolchain below.
-concurrent_links = exec_script("../get_concurrent_links.py", [], "value")
-
 # Parameters:
 #  current_cpu: current_cpu to pass as a build arg
 #  environment: File name of environment file.
 template("msvc_toolchain") {
-  if (defined(invoker.concurrent_links)) {
-    concurrent_links = invoker.concurrent_links
-  }
-
   env = invoker.environment
 
   if (is_debug) {
     configuration = "Debug"
   } else {
     configuration = "Release"
   }
   exec_script("../../vs_toolchain.py",
               [
                 "copy_dlls",
@@ skipping 129 matching lines @@
     }
 
     tool("copy") {
       command =
           "$python_path gyp-win-tool recursive-mirror {{source}} {{output}}"
       description = "COPY {{source}} {{output}}"
     }
 
     # When invoking this toolchain not as the default one, these args will be
     # passed to the build. They are ignored when this is the default toolchain.
-    toolchain_args() {
+    toolchain_args = {
       current_cpu = invoker.current_cpu
       if (defined(invoker.is_clang)) {
         is_clang = invoker.is_clang
       }
     }
   }
 }
 
 # TODO(dpranke): Declare both toolchains all of the time when we
 # get it sorted out how we want to support them both in a single build.
@@ skipping 25 matching lines @@
   }
   msvc_toolchain("clang_x64") {
     environment = "environment.x64"
     current_cpu = "x64"
     prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
                          root_build_dir)
     cl = "${goma_prefix}$prefix/clang-cl.exe"
     is_clang = true
   }
 }