Refactor stages 1, 2 and test_api overhaul.

scripts/slave/recipe_modules/auto_bisect/local_bisect.py

Index: scripts/slave/recipe_modules/auto_bisect/local_bisect.py
diff --git a/scripts/slave/recipe_modules/auto_bisect/local_bisect.py b/scripts/slave/recipe_modules/auto_bisect/local_bisect.py
index 0f4e6a97873287e6446ca8d19e34f14463810a66..a19adf846cdd10250c2325adcebdcb6fea1be61c 100644
--- a/scripts/slave/recipe_modules/auto_bisect/local_bisect.py
+++ b/scripts/slave/recipe_modules/auto_bisect/local_bisect.py
@@ -6,6 +6,7 @@ import base64
 import collections
 import json
 
+from . import exceptions
 
 def perform_bisect(api, **flags):
   # Try catch all the exceptions thrown in bisection so that recipe can
@@ -34,9 +35,13 @@ def perform_bisect(api, **flags):
             continue
           else:
             raise
-  except: # pylint: disable=bare-except
+  except exceptions.InconclusiveBisectException:
     if bisect_attempts:
-      bisect_attempts[-1].post_result(halt_on_failure=True)
+      bisect_attempts[-1].post_result()
+    raise api.m.step.StepFailure('Bisect cannot identify a culprit')
+  except Exception: # pylint: disable=bare-except
+    if bisect_attempts:
+      bisect_attempts[-1].post_result()
     raise
 
 def _perform_single_bisect(api, bisect_attempts, **flags):
@@ -47,9 +52,10 @@ def _perform_single_bisect(api, bisect_attempts, **flags):
       bisector = api.create_bisector(bisect_config, **flags)
       bisect_attempts.append(bisector)
       with api.m.step.nest('Gathering reference values'):
-        _gather_reference_range(api, bisector)
+        _gather_reference_range(bisector)
       if (not bisector.failed and bisector.check_improvement_direction() and
           bisector.check_initial_confidence()):
+        bisector.compute_relative_change()
         if bisector.check_reach_adjacent_revision(
             bisector.good_rev): # pragma: no cover
           # Only show this step if bisect has reached adjacent revisions.
@@ -68,22 +74,19 @@ def _get_connected_devices(api):
   api.m.chromium_android.device_status()
   return api.m.chromium_android.devices
 
-def _gather_reference_range(api, bisector):  # pragma: no cover
+def _gather_reference_range(bisector):  # pragma: no cover
   bisector.good_rev.start_job()
   bisector.bad_rev.start_job()
-  bisector.wait_for_all([bisector.good_rev, bisector.bad_rev])
   if bisector.good_rev.failed:
     bisector.surface_result('REF_RANGE_FAIL')
-    api.m.halt('Testing the "good" revision failed')
     bisector.failed = True
+    raise exceptions.InconclusiveBisectException(
+        'Testing the "good" revision failed')
   elif bisector.bad_rev.failed:
     bisector.surface_result('REF_RANGE_FAIL')
-    api.m.halt('Testing the "bad" revision failed')
     bisector.failed = True
-    api.m.halt('Testing the "good" revision failed')
-  else:
-    bisector.compute_relative_change()
-
+    raise exceptions.InconclusiveBisectException(
+        'Testing the "bad" revision failed')
 
 def _bisect_main_loop(bisector):  # pragma: no cover
   """This is the main bisect loop.
@@ -101,7 +104,6 @@ def _bisect_main_loop(bisector):  # pragma: no cover
                                       revision_to_check.revision_string())):
       bisector.post_result(halt_on_failure=False)
       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.