Update from https://crrev.com/305340

build/toolchain/win/setup_toolchain.py

 # 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 errno
 import os
 import re
 import subprocess
 import sys
 
 """
 Copies the given "win tool" (which the toolchain uses to wrap compiler
 invocations) and the environment blocks for the 32-bit and 64-bit builds on
 Windows to the build directory.
 
 The arguments are the visual studio install location and the location of the
 win tool. The script assumes that the root build directory is the current dir
 and the files will be written to the current directory.
 """
 
 
-def ExtractImportantEnvironment():
-  """Extracts environment variables required for the toolchain from the
-  current environment."""
+def _ExtractImportantEnvironment(output_of_set):
+  """Extracts environment variables required for the toolchain to run from
+  a textual dump output by the cmd.exe 'set' command."""
   envvars_to_save = (
-      'goma_.*',  # TODO(scottmg): This is ugly, but needed for goma.
-      'include',  # Needed by midl compiler.
+      'goma_.*', # TODO(scottmg): This is ugly, but needed for goma.
+      'include',
+      'lib',
+      'libpath',
       'path',
       'pathext',
       'systemroot',
       'temp',
       'tmp',
       )
-  result = {}
-  for envvar in envvars_to_save:
-    if envvar in os.environ:
-      envvar = envvar.lower()
-      if envvar == 'path':
-        # Our own rules (for running gyp-win-tool) and other actions in
-        # Chromium rely on python being in the path. Add the path to this
-        # python here so that if it's not in the path when ninja is run
-        # later, python will still be found.
-        result[envvar.upper()] = os.path.dirname(sys.executable) + \
-            os.pathsep + os.environ[envvar]
-      else:
-        result[envvar.upper()] = os.environ[envvar]
+  env = {}
+  for line in output_of_set.splitlines():
+    for envvar in envvars_to_save:
+      if re.match(envvar + '=', line.lower()):
+        var, setting = line.split('=', 1)
+        if envvar == 'path':
+          # Our own rules (for running gyp-win-tool) and other actions in
+          # Chromium rely on python being in the path. Add the path to this
+          # python here so that if it's not in the path when ninja is run
+          # later, python will still be found.
+          setting = os.path.dirname(sys.executable) + os.pathsep + setting
+        env[var.upper()] = setting
+        break
   for required in ('SYSTEMROOT', 'TEMP', 'TMP'):
-    if required not in result:
+    if required not in env:
       raise Exception('Environment variable "%s" '
                       'required to be set to valid path' % required)
-  return result
+  return env
 
 
-def FormatAsEnvironmentBlock(envvar_dict):
+def _SetupScript(target_arch, sdk_dir):
+  """Returns a command (with arguments) to be used to set up the
+  environment."""
+  # Check if we are running in the SDK command line environment and use
+  # the setup script from the SDK if so. |target_arch| should be either
+  # 'x86' or 'x64'.
+  assert target_arch in ('x86', 'x64')
+  if bool(int(os.environ.get('DEPOT_TOOLS_WIN_TOOLCHAIN', 1))) and sdk_dir:
+    return [os.path.normpath(os.path.join(sdk_dir, 'Bin/SetEnv.Cmd')),
+            '/' + target_arch]
+  else:
+    # We only support x64-hosted tools.
+    # TODO(scottmg|dpranke): Non-depot_tools toolchain: need to get Visual
+    # Studio install location from registry.
+    return [os.path.normpath(os.path.join(FIND_VS_IN_REG, 'VC/vcvarsall.bat')),
+            'amd64_x86' if target_arch == 'x86' else 'amd64']
+
+
+def _FormatAsEnvironmentBlock(envvar_dict):
   """Format as an 'environment block' directly suitable for CreateProcess.
   Briefly this is a list of key=value\0, terminated by an additional \0. See
   CreateProcess documentation for more details."""
   block = ''
   nul = '\0'
   for key, value in envvar_dict.iteritems():
     block += key + '=' + value + nul
   block += nul
   return block
 
 
-def CopyTool(source_path):
+def _CopyTool(source_path):
   """Copies the given tool to the current directory, including a warning not
   to edit it."""
   with open(source_path) as source_file:
     tool_source = source_file.readlines()
 
   # Add header and write it out to the current directory (which should be the
   # root build dir).
   with open("gyp-win-tool", 'w') as tool_file:
     tool_file.write(''.join([tool_source[0],
                              '# Generated by setup_toolchain.py do not edit.\n']
                             + tool_source[1:]))
 
-if len(sys.argv) != 4:
-  print('Usage setup_toolchain.py '
-        '<visual studio path> <win tool path> <win sdk path>')
-  sys.exit(2)
-vs_path = sys.argv[1]
-tool_source = sys.argv[2]
-win_sdk_path = sys.argv[3]
 
-CopyTool(tool_source)
+def main():
+  if len(sys.argv) != 5:
+    print('Usage setup_toolchain.py '
+          '<visual studio path> <win tool path> <win sdk path> <runtime dirs>')
+    sys.exit(2)
+  vs_path = sys.argv[1]
+  tool_source = sys.argv[2]
+  win_sdk_path = sys.argv[3]
+  runtime_dirs = sys.argv[4]
 
-important_env_vars = ExtractImportantEnvironment()
-path = important_env_vars["PATH"].split(";")
+  _CopyTool(tool_source)
 
-# Add 32-bit compiler path to the beginning and write the block.
-path32 = [os.path.join(vs_path, "VC\\BIN")] + \
-         [os.path.join(win_sdk_path, "bin\\x86")] + \
-         path
-important_env_vars["PATH"] = ";".join(path32)
-environ = FormatAsEnvironmentBlock(important_env_vars)
-with open('environment.x86', 'wb') as env_file:
-  env_file.write(environ)
+  archs = ('x86', 'x64')
+  # TODO(scottmg|goma): Do we need an equivalent of
+  # ninja_use_custom_environment_files?
+  for arch in archs:
+    # Extract environment variables for subprocesses.
+    args = _SetupScript(arch, win_sdk_path)
+    args.extend(('&&', 'set'))
+    popen = subprocess.Popen(
+        args, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+    variables, _ = popen.communicate()
+    env = _ExtractImportantEnvironment(variables)
+    env['PATH'] = runtime_dirs + ';' + env['PATH']
 
-# Add 64-bit compiler path to the beginning and write the block.
-path64 = [os.path.join(vs_path, "VC\\BIN\\amd64")] + \
-         [os.path.join(win_sdk_path, "bin\\x64")] + \
-         path
-important_env_vars["PATH"] = ";".join(path64)
-environ = FormatAsEnvironmentBlock(important_env_vars)
-with open('environment.x64', 'wb') as env_file:
-  env_file.write(environ)
+    # TODO(scottmg|thakis|dpranke): Is there an equivalent to
+    # msvs_system_include_dirs that we need to inject into INCLUDE here?
+
+    env_block = _FormatAsEnvironmentBlock(env)
+    with open('environment.' + arch, 'wb') as f:
+      f.write(env_block)
+
+
+if __name__ == '__main__':
+  main()