ios: fix cwd for git diff

scripts/slave/recipe_modules/chromium_tests/api.py

 # Copyright 2014 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 contextlib
 import copy
 import itertools
 import json
 
 from recipe_engine.types import freeze
@@ skipping 676 matching lines @@
       if deapply_patch:
         self.m.test_utils.determine_new_failures(api, tests, deapply_patch_fn)
       else:
         failing_tests = self.m.test_utils.run_tests_with_patch(api, tests)
         if failing_tests:
           self.m.python.failing_step(
               'test results',
               'TESTS FAILED; retries without patch disabled (%s)'
                   % deapply_patch_reason)
 
-  def get_files_affected_by_patch(self, relative_to='src/'):
+  def get_files_affected_by_patch(self, relative_to='src/', cwd=None):
     """Returns list of POSIX paths of files affected by patch for "analyze".
 
     Paths are relative to `relative_to` which for analyze should be 'src/'.
     """
     patch_root = self.m.gclient.calculate_patch_root(
         self.m.properties.get('patch_project'))
-    cwd = self._working_dir.join(patch_root) if self._working_dir else None
+    if not cwd:
+      cwd = self._working_dir.join(patch_root) if self._working_dir else None
     files = self.m.tryserver.get_files_affected_by_patch(patch_root, cwd=cwd)
     for i, path in enumerate(files):
       path = str(path)
       assert path.startswith(relative_to)
       files[i] = path[len(relative_to):]
     return files
 
   # TODO(phajdan.jr): fix callers and remove chromium_tests.configure_swarming.
   def configure_swarming(self, project_name, precommit, mastername=None):
     return self.m.chromium_swarming.configure_swarming(  # pragma: no cover
@@ skipping 102 matching lines @@
 
     if not tests:
       return
 
     api.chromium_swarming.configure_swarming(
         'chromium', precommit=False, mastername=mastername)
     test_runner = api.chromium_tests.create_test_runner(
         api, tests, serialize_tests=bot_config.get('serialize_tests'))
     with api.chromium_tests.wrap_chromium_tests(bot_config, tests):
       test_runner()