Return 0 when roll scripts terminate gracefully.

tools/push-to-trunk/common_includes.py

 #!/usr/bin/env python
 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
@@ skipping 638 matching lines @@
     state_file = "%s-state.json" % self._config[PERSISTFILE_BASENAME]
     if options.step == 0 and os.path.exists(state_file):
       os.remove(state_file)
 
     steps = []
     for (number, step_class) in enumerate(step_classes):
       steps.append(MakeStep(step_class, number, self._state, self._config,
                             options, self._side_effect_handler))
     for step in steps[options.step:]:
       if step.Run():
-        return 1
+        return 0
     return 0
 
   def Run(self, args=None):
     return self.RunSteps(self._Steps(), args)