Fix python scripts in src/chrome/

chrome/test/pyautolib/perf_snapshot.py

-#!/usr/bin/python
-
+#!/usr/bin/env python
 # Copyright (c) 2011 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.
 
 """Performance snapshot utility for pyauto tests.
 
 Wrapper around Chrome DevTools (mimics the front-end) to collect profiling info
 associated with a Chrome tab.  This script collects snapshots of the v8
 (Javascript engine) heap associated with the Chrome tab.
 
@@ skipping 850 matching lines @@
   snapshotter = PerformanceSnapshotter(
       tab_index=options.tab_index, output_file=options.output_file,
       interval=options.interval, num_snapshots=options.num_snapshots,
       verbose=options.verbose,
       show_socket_messages=options.show_socket_messages)
 
   if options.interactive_mode:
     snapshotter.SetInteractiveMode()
 
   snapshotter.HeapSnapshot()
+  return 0
 
 
 if __name__ == '__main__':
-  main()
+  sys.exit(main())