Add support for "additional_mirrors" property in trybot configs.

scripts/slave/recipes/findit/chromium/compile.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
 
 from recipe_engine.config import List
 from recipe_engine.config import Single
 from recipe_engine.recipe_api import Property
 
@@ skipping 32 matching lines @@
 class CompileResult(object):
   SKIPPED = 'skipped'  # No compile is needed.
   PASSED = 'passed'  # Compile passed.
   FAILED = 'failed'  # Compile failed.
 
 
 def _run_compile_at_revision(api, target_mastername, target_buildername,
                              revision, compile_targets, use_analyze):
   with api.step.nest('test %s' % str(revision)):
     # Checkout code at the given revision to recompile.
-    bot_update_step, master_dict, test_spec = \
+    bot_update_step, master_dicts, test_specs = \
         api.chromium_tests.prepare_checkout(
             target_mastername,
             target_buildername,
             root_solution_revision=revision)
 
     # TODO(http://crbug.com/560991): if compile targets are provided, check
     # whether they exist and then use analyze to compile the impacted ones by
     # the given revision.
     compile_targets = sorted(set(compile_targets or []))
     if not compile_targets:
       compile_targets, _ = api.chromium_tests.get_compile_targets_and_tests(
           target_mastername,
           target_buildername,
-          master_dict,
-          test_spec,
+          master_dicts,
+          None,
+          test_specs,
           override_bot_type='builder_tester')
 
       if use_analyze:
         changed_files = api.findit.files_changed_by_revision(revision)
 
         _, compile_targets = api.chromium_tests.analyze(
             changed_files,
             test_targets=[],
             additional_compile_targets=compile_targets,
             config_file_name='trybot_analyze_config.json',
             mb_mastername=target_mastername,
             mb_buildername=target_buildername,
             additional_names=None)
 
         if not compile_targets:
           # No compile target is impacted by the given revision.
           return CompileResult.SKIPPED
 
     try:
       api.chromium_tests.compile_specific_targets(
           target_mastername,
           target_buildername,
           bot_update_step,
-          master_dict,
+          master_dicts,
           compile_targets,
           tests_including_triggered=[],
           mb_mastername=target_mastername,
           mb_buildername=target_buildername,
           override_bot_type='builder_tester')
       return CompileResult.PASSED
     except api.step.InfraFailure:
       raise
     except api.step.StepFailure:
       return CompileResult.FAILED
@@ skipping 132 matching lines @@
                              })) +
       api.override_step_data(
           'test r1.analyze',
           api.json.output({
               'status': 'Found dependency',
               'compile_targets': ['a', 'a_run'],
               'test_targets': ['a', 'a_run'],
           })
       )
   )