Change clang_format.py to search for clang-format in buildtools

clang_format.py

 #!/usr/bin/env python
 # 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.
 
 """Redirects to the version of clang-format checked into the Chrome tree.
 
 clang-format binaries are pulled down from Google Cloud Storage whenever you
 sync Chrome, to platform-specific locations. This script knows how to locate
 those tools, assuming the script is invoked from inside a Chromium checkout."""
 
 import gclient_utils
 import os
 import subprocess
 import sys
 
 
 class NotFoundError(Exception):
   """A file could not be found."""
   def __init__(self, e):
     Exception.__init__(self,
         'Problem while looking for clang-format in Chromium source tree:\n'
         '  %s' % e)
 
 
-def _FindChromiumSourceRoot():
-  """Return the source root of the current chromium checkout, or die trying."""
-  # The use of .gn is somewhat incongruous here, but we need a file uniquely
-  # existing at src/. GN does the same thing at least.
-  source_root = gclient_utils.FindFileUpwards('.gn')
-  if not source_root:
-    raise NotFoundError(
-        '.gn file not found in any parent of the current path.')
-  return source_root
-
-
 def FindClangFormatToolInChromiumTree():
   """Return a path to the clang-format executable, or die trying."""
-  tool_path = os.path.join(_FindChromiumSourceRoot(), 'third_party',
-                           'clang_format', 'bin',
-                           gclient_utils.GetMacWinOrLinux(),
+  bin_path = gclient_utils.GetBuildtoolsPlatformBinaryPath()
+  if not bin_path:
+    raise NotFoundError(
+        'Could not find checkout in any parent of the current path.')
+
+  tool_path = os.path.join(bin_path,
                            'clang-format' + gclient_utils.GetExeSuffix())
   if not os.path.exists(tool_path):
     raise NotFoundError('File does not exist: %s' % tool_path)
   return tool_path
 
 
 def FindClangFormatScriptInChromiumTree(script_name):
   """Return a path to a clang-format helper script, or die trying."""
-  script_path = os.path.join(_FindChromiumSourceRoot(), 'third_party',
-                             'clang_format', 'script', script_name)
+  tools_path = gclient_utils.GetBuildtoolsPath()
+  if not tools_path:
+    raise NotFoundError(
+        'Could not find checkout in any parent of the current path.')
+  script_path = os.path.join(tools_path, 'clang_format', 'script', script_name)
   if not os.path.exists(script_path):
     raise NotFoundError('File does not exist: %s' % script_path)
   return script_path
 
 
 def main(args):
   try:
     tool = FindClangFormatToolInChromiumTree()
   except NotFoundError, e:
     print >> sys.stderr, e
     sys.exit(1)
 
   # Add some visibility to --help showing where the tool lives, since this
   # redirection can be a little opaque.
   help_syntax = ('-h', '--help', '-help', '-help-list', '--help-list')
   if any(match in args for match in help_syntax):
     print '\nDepot tools redirects you to the clang-format at:\n    %s\n' % tool
 
   return subprocess.call([tool] + sys.argv[1:])
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))