Add support for VS express to the GN build.

build/vs_toolchain.py

 # Copyright 2014 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 json
 import os
 import pipes
 import shutil
 import subprocess
 import sys
@@ skipping 123 matching lines @@
                     'get_toolchain_if_necessary.py'),
         '--output-json', json_data_file,
       ] + _GetDesiredVsToolchainHashes()
     subprocess.check_call(get_toolchain_args)
 
   return 0
 
 
 def GetToolchainDir():
   """Gets location information about the current toolchain (must have been
-  previously updated by 'update')."""
+  previously updated by 'update'). This is used for the GN build."""
   SetEnvironmentAndGetRuntimeDllDirs()
-  print '["%s", "%s"]' % (
-      os.environ['GYP_MSVS_OVERRIDE_PATH'], os.environ['WINDOWSSDKDIR'])
+  print '''vs_path = "%s"
+sdk_path = "%s"
+vs_version = "%s"
+wdk_dir = "%s"
+''' % (
+      os.environ['GYP_MSVS_OVERRIDE_PATH'],
+      os.environ['WINDOWSSDKDIR'],
+      os.environ['GYP_MSVS_VERSION'],
+      os.environ['WDK_DIR'])
 
 
 def main():
   if not sys.platform.startswith(('win32', 'cygwin')):
     return 0
   commands = {
       'update': Update,
       'get_toolchain_dir': GetToolchainDir,
       # TODO(scottmg): Add copy_dlls for GN builds (gyp_chromium calls
       # CopyVsRuntimeDlls via import, currently).
   }
   if len(sys.argv) < 2 or sys.argv[1] not in commands:
     print >>sys.stderr, 'Expected one of: %s' % ', '.join(commands)
     return 1
   return commands[sys.argv[1]]()
 
 
 if __name__ == '__main__':
   sys.exit(main())