Flip remaining chromium_gn bots to the chromium recipe.

scripts/slave/recipe_modules/chromium/test_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.
 
 from recipe_engine import recipe_test_api
 
 
 class ChromiumTestApi(recipe_test_api.RecipeTestApi):
   def gen_tests_for_builders(self, builder_dict, overrides=None):
     # TODO: crbug.com/354674. Figure out where to put "simulation"
@@ skipping 18 matching lines @@
         )
         if mastername.startswith('tryserver'):
           test += self.m.properties.tryserver(buildername=buildername,
                                               mastername=mastername)
         else:
           test += self.m.properties.generic(buildername=buildername,
                                             mastername=mastername)
 
         override_step_data = overrides.get(mastername, {}).get(buildername,
                                                                None)
-        if override_step_data:
-            test += override_step_data
+        if override_step_data:  # pragma: nocover
+          # No tests currently use this, but it would be really
+          # confusing if 'override_step_data' wasn't supported.
+          test += override_step_data
         yield test
 
   # The following data was generated by running 'gyp_chromium
   # --analyzer' with input JSON files corresponding to changes
   # affecting these targets.
   @property
   def analyze_builds_nothing(self):
     return self.m.json.output({
         'status': 'No dependencies',
         'compile_targets': [],
         'test_targets': [],
         })