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

tools/telemetry/telemetry/value/__init__.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.
 """
 The Value hierarchy provides a way of representing the values measurements
 produce such that they can be merged across runs, grouped by page, and output
 to different targets.
 
 The core Value concept provides the basic functionality:
 - association with a page, may be none
 - naming and units
 - importance tracking [whether a value will show up on a waterfall or output
   file by default]
 - other metadata, such as a description of what was measured
 - default conversion to scalar and string
 - merging properties
 
 A page may actually run a few times during a single telemetry session.
 Downstream consumers of test results typically want to group these runs
 together, then compute summary statistics across runs. Value provides the
 Merge* family of methods for this kind of aggregation.
 """
 import os
 
+from telemetry.core import discover
 from telemetry.core import util
-from telemetry.util import classes_util
-
 
 # When combining a pair of Values togehter, it is sometimes ambiguous whether
 # the values should be concatenated, or one should be picked as representative.
 # The possible merging policies are listed here.
 CONCATENATE = 'concatenate'
 PICK_FIRST = 'pick-first'
 
 # When converting a Value to its buildbot equivalent, the context in which the
 # value is being interpreted actually affects the conversion. This is insane,
 # but there you have it. There are three contexts in which Values are converted
@@ skipping 204 matching lines @@
 
     Given a list of value dicts produced by AsDict, this method
     deserializes the dicts given a dict mapping page IDs to pages.
     This method performs memoization for deserializing a list of values
     efficiently, where FromDict is meant to handle one-offs.
 
     values: a list of value dicts produced by AsDict() on a value subclass.
     page_dict: a dictionary mapping IDs to page objects.
     """
     value_dir = os.path.dirname(__file__)
-    value_classes = classes_util.DiscoverClassesByClassName(
-        value_dir, util.GetTelemetryDir(), Value)
+    value_classes = discover.DiscoverClasses(
+        value_dir, util.GetTelemetryDir(),
+        Value, index_by_class_name=True)
 
     value_json_types = dict((value_classes[x].GetJSONTypeName(), x) for x in
         value_classes)
 
     values = []
     for value_dict in value_dicts:
       value_class = value_classes[value_json_types[value_dict['type']]]
       assert 'FromDict' in value_class.__dict__, \
              'Subclass doesn\'t override FromDict'
       values.append(value_class.FromDict(value_dict, page_dict))
@@ skipping 63 matching lines @@
   whereas telemetry represents values with a chart_name.trace_name convention,
   where chart_name is optional. This convention is also used by chart_json.
 
   This converts from the telemetry convention to the buildbot convention,
   returning a 2-tuple (measurement_name, trace_name).
   """
   if '.' in value_name:
     return value_name.split('.', 1)
   else:
     return value_name, value_name