Track step nesting in StreamEngine.

recipes.py

 #!/usr/bin/env python
 # Copyright 2015 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.
 
 """Tool to interact with recipe repositories.
 
 This tool operates on the nearest ancestor directory containing an
 infra/config/recipes.cfg.
 """
@@ skipping 136 matching lines @@
       os.path.join(os.path.dirname(os.path.realpath(__file__)), 'workdir'))
   logging.info('Using %s as work directory' % workdir)
   if not os.path.exists(workdir):
     os.makedirs(workdir)
 
   old_cwd = os.getcwd()
   os.chdir(workdir)
   stream_engine = stream.ProductStreamEngine(
       stream.StreamEngineInvariants(),
       stream.AnnotatorStreamEngine(
-        sys.stdout, emit_timestamps=(args.timestamps or
-                                     op_args.annotation_flags.emit_timestamp)))
+        sys.stdout,
+        emit_timestamps=(args.timestamps or
+                         op_args.annotation_flags.emit_timestamp)))
   with stream_engine:
     # Emit initial properties if configured to do so.
     if op_args.annotation_flags.emit_initial_properties:
       with stream_engine.new_step_stream('Initial Properties') as s:
         for key in sorted(properties.iterkeys()):
           s.set_build_property(key, json.dumps(properties[key], sort_keys=True))
 
     try:
       ret = recipe_run.run_steps(
           properties, stream_engine,
@@ skipping 397 matching lines @@
   ret = main()
   if not isinstance(ret, int):
     if ret is None:
       ret = 0
     else:
       print >> sys.stderr, ret
       ret = 1
   sys.stdout.flush()
   sys.stderr.flush()
   os._exit(ret)