Histograms.xml python script housekeeping

tools/metrics/histograms/validate_format.py

 #!/usr/bin/env python
 # Copyright 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.
 
 """Verifies that the histograms XML file is well-formatted."""
 
+import os
+import sys
+
+sys.path.append(os.path.join(os.path.dirname(__file__), '..', 'common'))
+import path_util
+
 import extract_histograms
-import os.path
-
 
 def main():
   # This will raise an exception if the file is not well-formatted.
-  xml_file = os.path.join(os.path.dirname(os.path.realpath(__file__)),
-                          'histograms.xml')
+  xml_file = path_util.GetHistogramsFile()
   histograms = extract_histograms.ExtractHistograms(xml_file)
 
 
 if __name__ == '__main__':
   main()