Fix python scripts in src/chrome/

chrome/tools/extract_histograms.py

-#!/usr/bin/python
+#!/usr/bin/env python
 # Copyright (c) 2009 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.
 
 """Extract UMA histogram strings from the Chrome source.
 
 This program generates the list of known histograms we expect to see in
 the user behavior logs.  It walks the Chrome source, looking for calls
 to UMA histogram macros.
 
@@ skipping 16 matching lines @@
     path: path to the file
     histograms: set of histograms to add to
   """
 
   histogram_re = re.compile(r'HISTOGRAM_\w+\(L"(.*)"')
   for line in open(path):
     match = histogram_re.search(line)
     if match:
       histograms.add(match.group(1))
 
+
 def WalkDirectory(root_path, histograms):
   for path, dirs, files in os.walk(root_path):
     if '.svn' in dirs:
       dirs.remove('.svn')
     for file in files:
       ext = os.path.splitext(file)[1]
       if ext == '.cc':
         GrepForHistograms(os.path.join(path, file), histograms)
 
+
 def main(argv):
   histograms = set()
 
   # Walk the source tree to process all .cc files.
   WalkDirectory('..', histograms)
 
   # Print out the histograms as a sorted list.
   for histogram in sorted(histograms):
     print histogram
+  return 0
+
 
 if '__main__' == __name__:
-  main(sys.argv)
+  sys.exit(main(sys.argv))