Avoid nesting steps called under waiting for x:

scripts/slave/recipe_modules/auto_bisect/local_bisect.py

 # Copyright 2015 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 base64
 import collections
 import json
 
 
-def perform_bisect(api):  # pragma: no cover
+def perform_bisect(api, **flags):  # pragma: no cover
   bisect_config = api.m.properties.get('bisect_config')
   assert isinstance(bisect_config, collections.Mapping)
-  bisector = api.create_bisector(bisect_config)
+  bisector = api.create_bisector(bisect_config, **flags)
   with api.m.step.nest('Gathering reference values'):
     _gather_reference_range(api, bisector)
   if (not bisector.failed and bisector.check_improvement_direction() and
       bisector.check_initial_confidence()):
     if bisector.check_reach_adjacent_revision(bisector.good_rev):
       # Only show this step if bisect has reached adjacent revisions.
       with api.m.step.nest(str('Check bisect finished on revision ' +
                                bisector.good_rev.revision_string())):
         if bisector.check_bisect_finished(bisector.good_rev):
           bisector.bisect_over = True
@@ skipping 40 matching lines @@
       revision_to_check.start_job()
       bisector.wait_for(revision_to_check)
 
     if bisector.check_reach_adjacent_revision(revision_to_check):
       # Only show this step if bisect has reached adjacent revisions.
       with bisector.api.m.step.nest(
           str('Check bisect finished on revision ' +
               revision_to_check.revision_string())):
         if bisector.check_bisect_finished(revision_to_check):
             bisector.bisect_over = True