Avoid nesting steps called under waiting for x:

scripts/slave/recipe_modules/auto_bisect/bisector.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 json
 import re
 import time
 import urllib
 
 from . import config_validation
@@ skipping 50 matching lines @@
 
 _DIRECTION_OF_IMPROVEMENT_ABORT_REASON = (
     'The metric values for the initial "good" and "bad" revisions match the '
     'expected direction of improvement. Thus, likely represent an improvement '
     'and not a regression.')
 
 
 class Bisector(object):
   """This class abstracts an ongoing bisect (or n-sect) job."""
 
-  def __init__(self, api, bisect_config, revision_class, init_revisions=True):
+  def __init__(self, api, bisect_config, revision_class, init_revisions=True,
+               **flags):
     """Initializes the state of a new bisect job from a dictionary.
 
     Note that the initial good_rev and bad_rev MUST resolve to a commit position
     in the chromium repo.
     """
     super(Bisector, self).__init__()
+    self.flags = flags
     self._api = api
     self.result_codes = set()
     self.ensure_sync_master_branch()
     self.bisect_config = bisect_config
     self.config_step()
     self._validate_config()
     self.revision_class = revision_class
     self.last_tested_revision = None
 
     # Test-only properties.
@@ skipping 647 matching lines @@
         return False
       self.culprit = revision.next_revision
       return True
     return False
 
   def wait_for_all(self, revision_list):
     """Waits for all revisions in list to finish."""
     for r in revision_list:
       self.wait_for(r)
 
-  def wait_for(self, revision):
+  def wait_for(self, revision, nest_check=True):
     """Waits for the revision to finish its job."""
-    with self.api.m.step.nest('Waiting for ' + revision.revision_string()):
-      while True:
-        revision.update_status()
-        if revision.in_progress:
-          self.api.m.python.inline(
-              'sleeping',
-              """
-              import sys
-              import time
-              time.sleep(20*60)
-              sys.exit(0)
-              """)
-        else:
-          break
+    if nest_check and not self.flags.get(
+        'do_not_nest_wait_for_revision'):  # pragma: no cover
+      with self.api.m.step.nest('Waiting for ' + revision.revision_string()):
+        return self.wait_for(revision, nest_check=False)
+    while True:
+      revision.update_status()
+      if revision.in_progress:
+        self.api.m.python.inline(
+            'sleeping',
+            """
+            import sys
+            import time
+            time.sleep(20*60)
+            sys.exit(0)
+            """)
+      else:
+        break
 
   def _update_candidate_range(self):
     """Updates lkgr and fkbr (last known good/first known bad) revisions.
 
     lkgr and fkbr are 'pointers' to the appropriate RevisionState objects in
     bisectors.revisions."""
     for r in self.revisions:
       if r.tested:
         if r.good:
           self.lkgr = r
@@ skipping 169 matching lines @@
         })
     return revision_rows
 
   def _get_build_url(self):
     properties = self.api.m.properties
     bot_url = properties.get('buildbotURL',
                              'http://build.chromium.org/p/chromium/')
     builder_name = urllib.quote(properties.get('buildername', ''))
     builder_number = str(properties.get('buildnumber', ''))
     return '%sbuilders/%s/builds/%s' % (bot_url, builder_name, builder_number)