Fix python scripts in src/tools/

tools/traceline/traceline/scripts/crit_sec.py

+#!/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.
 
 import sys
 import os
 
-execfile(os.path.join(
-  os.path.dirname(os.path.join(os.path.curdir, __file__)),
-  'syscalls.py'))
+from syscalls import syscalls
+
 
 def parseEvents(z):
   crits =  { }
   calls = { }
   for e in z:
     if (e['eventtype'] == 'EVENT_TYPE_ENTER_CS' or
         e['eventtype'] == 'EVENT_TYPE_TRYENTER_CS' or
         e['eventtype'] == 'EVENT_TYPE_LEAVE_CS'):
       cs = e['critical_section']
       if not crits.has_key(cs):
@@ skipping 20 matching lines @@
           raise repr(e)
         tid = tid_stack.pop()
         if tid['thread'] != e['thread']:
           raise repr(tid) + '--' + repr(e)
 
     # Critical section left locked?
     if tid_stack:
       #raise repr(tid_stack)
       pass
 
-execfile(sys.argv[1])
+
+def main():
+  execfile(sys.argv[1])
+
+
+if __name__ == '__main__':
+  main()