[Protobuf] Add <map> include to workaround a gcc bug

tools/mb/mb.py

 #!/usr/bin/env python
 # Copyright 2015 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.
 
 """MB - the Meta-Build wrapper around GYP and GN
 
 MB is a wrapper script for GYP and GN that can be used to generate build files
 for sets of canned configurations and analyze them.
 """
 
+# TODO(thomasanderson): Remove this comment.  It is added to
+# workaround https://crbug.com/736215 for CL
+# https://codereview.chromium.org/2974603002/
+
 from __future__ import print_function
 
 import argparse
 import ast
 import errno
 import json
 import os
 import pipes
 import pprint
 import re
@@ skipping 1517 matching lines @@
   # Then check to see if the arg contains any metacharacters other than
   # double quotes; if it does, quote everything (including the double
   # quotes) for safety.
   if any(a in UNSAFE_FOR_CMD for a in arg):
     arg = ''.join('^' + a if a in ALL_META_CHARS else a for a in arg)
   return arg
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))