Swarming: conditionally run tests on swarming in chromium_trybot recipe.

scripts/slave/recipe_modules/isolate/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 slave import recipe_test_api
 
 class IsolateTestApi(recipe_test_api.RecipeTestApi):
   def output_json(self, targets=None):
-    """Mocked output or find_isolated_tests.py script.
+    """Mocked output of find_isolated_tests.py script.
 
-    Deterministically synthesized json.output test data for the given targets.
+    Deterministically synthesizes json.output test data for the given targets.
     If |targets| is None, will emit test data with some dummy targets instead,
     emulating find_isolated_tests.py finding some files.
     """
     if targets is None:
       targets = ['dummy_target_1', 'dummy_target_2']
     return self.m.json.output(dict(
         (target, '[dummy hash for %s]' % target) for target in targets))