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

tools/perf/measurements/measurement_smoke_test.py

Index: tools/perf/measurements/measurement_smoke_test.py
diff --git a/tools/perf/measurements/measurement_smoke_test.py b/tools/perf/measurements/measurement_smoke_test.py
index a8c8477844b3999cdef1279ae4cf64a8df20fb7d..bedd0ba05582bbdea8a58de9453d4f502f781108 100644
--- a/tools/perf/measurements/measurement_smoke_test.py
+++ b/tools/perf/measurements/measurement_smoke_test.py
@@ -8,10 +8,10 @@
 import unittest
 
 from telemetry import benchmark as benchmark_module
+from telemetry.core import discover
 from telemetry.internal.browser import browser_options
 from telemetry.page import page_test
 from telemetry.testing import options_for_unittests
-from telemetry.util import classes_util
 from telemetry.web_perf import timeline_based_measurement
 
 
@@ -23,14 +23,14 @@
 
   # Get all page test instances from measurement classes that are directly
   # constructable
-  all_measurement_classes = classes_util.DiscoverClasses(
+  all_measurement_classes = discover.DiscoverClasses(
       measurements_dir, top_level_dir, page_test.PageTest,
-      directly_constructable=True)
+      index_by_class_name=True, directly_constructable=True).values()
   for measurement_class in all_measurement_classes:
     page_test_instances.append(measurement_class())
 
-  all_benchmarks_classes = classes_util.DiscoverClasses(
-      benchmarks_dir, top_level_dir, benchmark_module.Benchmark)
+  all_benchmarks_classes = discover.DiscoverClasses(
+      benchmarks_dir, top_level_dir, benchmark_module.Benchmark).values()
 
   # Get all page test instances from defined benchmarks.
   # Note: since this depends on the command line options, there is no guaranteed