Track step nesting in StreamEngine.

recipe_modules/generator_script/api.py

 # Copyright 2013 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 from recipe_engine import recipe_api
 
 class GeneratorScriptApi(recipe_api.RecipeApi):
   def __call__(self, path_to_script, *args, **kwargs):
     """Run a script and generate the steps emitted by that script.
 
@@ skipping 72 matching lines @@
         step['env'] = new_env
       outputs_json = step.pop('outputs_presentation_json', False)
       if outputs_json:
         # This step has requested a JSON file which the binary that
         # it invokes can write to, so provide it with one.
         step['cmd'].extend(['--presentation-json', self.m.json.output(False)])
 
       #TODO(martiniss) change this to use a regular step call
       step['ok_ret'] = set(step.pop('ok_ret', {0}))
       step['infra_step'] = bool(step.pop('infra_step', False))
-      step['step_nest_level'] = int(step.pop('step_nest_level', 0))
+      step['step_nest_level'] = step.pop('step_nest_level', 0)
 
       if step.pop('always_run', False) or not failed_steps:
         try:
           self.m.step.run_from_dict(step)
         except self.m.step.StepFailure:
           failed_steps.append(step['name'])
         finally:
           step_result = self.m.step.active_result
           if outputs_json:
             p = step_result.presentation
             j = step_result.json.output
 
             if j:
               p.logs.update(j.get('logs', {}))
               p.links.update(j.get('links', {}))
               p.step_summary_text = j.get('step_summary_text', '')
               p.step_text = j.get('step_text', '')
               p.properties.update(j.get('properties', {}))
 
     if failed_steps:
       raise self.m.step.StepFailure(
         "the following steps in %s failed: %s" %
         (step_name, failed_steps))