Fix python scripts in src/tools/

tools/traceline/traceline/scripts/alloc.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
 
-execfile(os.path.join(
-  os.path.dirname(os.path.join(os.path.curdir, __file__)),
-  'syscalls.py'))
+from syscalls import syscalls
 
 def parseEvents(z):
   calls = { }
   for e in z:
     if e['eventtype'] == 'EVENT_TYPE_SYSCALL' and e['syscall'] == 17:
       delta = e['done'] - e['ms']
       tid = e['thread']
       ms = e['ms']
       print '%f - %f - %x' % (
           delta, ms, tid)
 
-execfile(sys.argv[1])
+
+def main():
+  execfile(sys.argv[1])
+
+
+if __name__ == '__main__':
+  sys.exit(main())