Drop unwanted dependencies on chromium_tests recipe module

scripts/slave/recipes/chromium_trybot.py

 # Copyright 2013 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 collections
 
 from recipe_engine.types import freeze
 
 DEPS = [
   'depot_tools/bot_update',
   'chromium',
   'chromium_android',
+  'chromium_checkout',
   'chromium_swarming',
   'chromium_tests',
   'commit_position',
   'file',
   'filter',
   'depot_tools/gclient',
   'isolate',
   'recipe_engine/json',
   'recipe_engine/path',
   'recipe_engine/platform',
@@ skipping 85 matching lines @@
   bot_update_step, bot_db = api.chromium_tests.prepare_checkout(
       bot_config_object)
 
   tests, tests_including_triggered = api.chromium_tests.get_tests(
       bot_config_object, bot_db)
 
   def add_tests(additional_tests):
     tests.extend(additional_tests)
     tests_including_triggered.extend(additional_tests)
 
-  affected_files = api.chromium_tests.get_files_affected_by_patch('src/')
+  affected_files = api.chromium_checkout.get_files_affected_by_patch('src/')
 
   affects_blink_paths = any(
       f.startswith(path) for f in affected_files
       for path in CHROMIUM_BLINK_TESTS_PATHS)
   affects_blink = any(
       f.startswith('third_party/WebKit') for f in affected_files)
 
   if affects_blink:
     subproject_tag = 'blink'
   elif affects_blink_paths:
@@ skipping 793 matching lines @@
     props(mastername='tryserver.v8',
           buildername='v8_linux_blink_rel',
           patch_project='v8') +
     api.platform.name('linux') +
     suppress_analyze(more_exclusions=['v8/f.*']) +
     api.override_step_data('webkit_tests (with patch)',
         api.test_utils.canned_test_output(passing=False)) +
     api.override_step_data('webkit_tests (without patch)',
         api.test_utils.canned_test_output(passing=True, minimal=True))
   )