Create classes_util API, change discover to return a list instead of a dict.

tools/telemetry/telemetry/testing/story_set_smoke_test.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 logging
 import os
 import unittest
 
-from telemetry.core import discover
 from telemetry.internal.browser import browser_credentials
 from telemetry import page
 from telemetry import story as story_module
+from telemetry.util import classes_util
 from telemetry.wpr import archive_info
 
 
 class StorySetSmokeTest(unittest.TestCase):
 
   def setUp(self):
     # Make sure the added failure message is appended to the default failure
     # message.
     self.longMessage = True
 
   def GetAllStorySetClasses(self, story_sets_dir, top_level_dir):
     # We can't test page sets that aren't directly constructable since we
     # don't know what arguments to put for the constructor.
-    return discover.DiscoverClasses(story_sets_dir, top_level_dir,
-                                    story_module.StorySet,
-                                    directly_constructable=True).values()
+    return classes_util.DiscoverClasses(story_sets_dir, top_level_dir,
+                                        story_module.StorySet,
+                                        directly_constructable=True)
 
   def CheckArchive(self, story_set):
     """Verify that all URLs of pages in story_set have an associated archive."""
     # TODO: Eventually these should be fatal.
     if not story_set.archive_data_file:
       logging.warning('Skipping %s: no archive data file', story_set.file_path)
       return
 
     logging.info('Testing %s', story_set.file_path)
 
@@ skipping 95 matching lines @@
     method to run smoke test.
     """
     story_sets = self.GetAllStorySetClasses(story_sets_dir, top_level_dir)
     for story_set_class in story_sets:
       story_set = story_set_class()
       logging.info('Testing %s', story_set.file_path)
       self.CheckArchive(story_set)
       self.CheckCredentials(story_set)
       self.CheckAttributes(story_set)
       self.CheckSharedStates(story_set)