Update from https://crrev.com/306655

tools/clang/scripts/run_tool.py

 #!/usr/bin/env python
 # 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.
 
 """Wrapper script to help run clang tools across Chromium code.
 
 How to use this tool:
 If you want to run the tool across all Chromium code:
 run_tool.py <tool> <path/to/compiledb>
@@ skipping 296 matching lines @@
       os.path.dirname(os.path.realpath(__file__)),
       '../../../third_party/llvm/tools/clang/tools/clang-format',
       'clang-format-diff.py')
   # TODO(dcheng): Allow this to be controlled with a flag as well.
   # TODO(dcheng): Shell escaping of args to git diff to clang-format is broken
   # on Windows.
   if not os.path.isfile(clang_format_diff_path) or sys.platform == 'win32':
     clang_format_diff_path = None
 
   if len(argv) == 3 and argv[2] == '--all':
-    filenames = frozenset(_GetFilesFromCompileDB(argv[1]))
+    filenames = set(_GetFilesFromCompileDB(argv[1]))
   else:
-    filenames = frozenset(_GetFilesFromGit(argv[2:]))
-  # Filter out files that aren't C/C++/Obj-C/Obj-C++.
-  extensions = frozenset(('.c', '.cc', '.m', '.mm'))
-  dispatcher = _CompilerDispatcher(argv[0], argv[1],
-                                   [f for f in filenames
-                                    if os.path.splitext(f)[1] in extensions])
+    filenames = set(_GetFilesFromGit(argv[2:]))
+    # Filter out files that aren't C/C++/Obj-C/Obj-C++.
+    extensions = frozenset(('.c', '.cc', '.m', '.mm'))
+    filenames = [f for f in filenames
+                 if os.path.splitext(f)[1] in extensions]
+  dispatcher = _CompilerDispatcher(argv[0], argv[1], filenames)
   dispatcher.Run()
   # Filter out edits to files that aren't in the git repository, since it's not
   # useful to modify files that aren't under source control--typically, these
   # are generated files or files in a git submodule that's not part of Chromium.
   _ApplyEdits({k : v for k, v in dispatcher.edits.iteritems()
                     if os.path.realpath(k) in filenames},
               clang_format_diff_path)
   if dispatcher.failed_count != 0:
     return 2
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))