Add support for "additional_mirrors" property in trybot configs.

scripts/slave/recipe_modules/auto_bisect/api.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.
 
 """API for the bisect recipe module.
 
 This API is meant to enable the bisect recipe to bisect any chromium-supported
 platform for any test that can be run via buildbot, perf or otherwise.
 """
 
@@ skipping 113 matching lines @@
         self.m.path['checkout'].join('tools', 'run-bisect-perf-regression.py'),
         ['-w', self.m.path['slave_build']] + args,
         name='Running Bisection',
         xvfb=True, **kwargs)
 
   def run_local_test_run(self, api, test_config_params):  # pragma: no cover
     mastername = api.properties.get('mastername')
     buildername = api.properties.get('buildername')
     api.chromium_tests.configure_build(mastername, buildername)
     api.gclient.apply_config('perf')
-    update_step, master_dict, _ = \
+    update_step, master_dicts, _ = \
         api.chromium_tests.prepare_checkout(
             mastername, buildername,
             root_solution_revision=test_config_params['revision'])
-    self.start_test_run_for_bisect(api, update_step, master_dict,
+    self.start_test_run_for_bisect(api, update_step, master_dicts[0],

[luqui, 2016/01/05 23:02:35]

This [0] is suspicious.  Is it clear during construction that the first element
is distinguished in this way (or does it not matter for some reason)?

[Ken Russell (switch to Gerrit), 2016/01/06 00:38:24]

No, I didn't do a good job documenting the return values from
api.chromium_tests.prepare_checkout. I agree this approach is pretty hacky.
Basically, I found it necessary to return multiple master_dicts and test_specs
from prepare_checkout, so both return values are arrays now. The first entry in
each array is what would previously have been returned in master_dict and
test_spec. Subsequent entries correspond to the "additional_mirrors" entry in
trybots.py.

I may have missed something major in the design here, but it does seem to me
that it's necessary to return both multiple master_dict and test_spec instances.
However, api.chromium_tests.get_master_dict_with_dynamic_tests does some work
which makes me wonder if all the data in test_spec is actually embedded already
in the returned master_dict instance.

[Sergey Berezin, 2016/01/06 01:50:56]

I suspect that bisect would only run waterfall builders, which would only have
one entry in master_dicts. I feel it'd be cleaner to modify
start_test_run_for_bisect() to take master_dicts, but that would probably
trigger too much other code change... 

I'm actually not sure what would be a simple good solution here.

                                    test_config_params, run_locally=True)
 
   def start_test_run_for_bisect(self, api, update_step, master_dict,
                                 test_config_params, run_locally=False):
     mastername = api.properties.get('mastername')
     buildername = api.properties.get('buildername')
     bot_config = master_dict.get('builders', {}).get(buildername)
     if not run_locally:
       api.bisect_tester.upload_job_url()
     if api.chromium.c.TARGET_PLATFORM == 'android':
@@ skipping 85 matching lines @@
                                          api.properties)
       else:
         self.m.perf_try.start_perf_try_job(
             affected_files, update_step, master_dict)
     finally:
       # Avoid duplication of device setup steps for bisect recipe tester, which
       # are run while running tests in chromium_tests.wrap_chromium_tests.
       if (api.properties.get('bisect_config') is None and
           api.chromium.c.TARGET_PLATFORM == 'android'):
         api.chromium_android.common_tests_final_steps()