Fix python scripts in src/tools/

tools/traceline/traceline/scripts/filter_short.py

Index: tools/traceline/traceline/scripts/filter_short.py
diff --git a/tools/traceline/traceline/scripts/filter_short.py b/tools/traceline/traceline/scripts/filter_short.py
index 9d8466ed1f1a4f92a75369ad23cf057374aebe3f..c733789e5c453b70434ebca51448137a0d52f9f3 100755
--- a/tools/traceline/traceline/scripts/filter_short.py
+++ b/tools/traceline/traceline/scripts/filter_short.py
@@ -1,14 +1,17 @@
+#!/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.
 
-# This script takes an input JSON, and filters out all system call events that
-# took less than 0.2ms.  This helps trim down the JSON data to only the most
-# interesting / time critical events.
+"""This script takes an input JSON, and filters out all system call events that
+took less than 0.2ms.  This helps trim down the JSON data to only the most
+interesting / time critical events.
+"""
 
 import sys
 import re
 
+
 def parseEvents(z):
   print 'parseEvents(['
   for e in z:
@@ -20,4 +23,10 @@ def parseEvents(z):
     print '%s,' % re.sub('([0-9])L\\b', '\\1', str(e))
   print '])'
 
-execfile(sys.argv[1])
+
+def main():
+  execfile(sys.argv[1])
+
+
+if __name__ == '__main__':
+  main()