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

tools/telemetry/telemetry/internal/util/find_dependencies.py

Index: tools/telemetry/telemetry/internal/util/find_dependencies.py
diff --git a/tools/telemetry/telemetry/internal/util/find_dependencies.py b/tools/telemetry/telemetry/internal/util/find_dependencies.py
index 2082565ea83ad0671204fac62240b4fc6b4a82d6..b45cf78b059ae5b504da0e665a12e097a828e705 100644
--- a/tools/telemetry/telemetry/internal/util/find_dependencies.py
+++ b/tools/telemetry/telemetry/internal/util/find_dependencies.py
@@ -13,11 +13,12 @@ import zipfile
 
 from catapult_base import cloud_storage
 from telemetry import benchmark
-from telemetry.core import discover
 from telemetry.internal.util import bootstrap
 from telemetry.internal.util import command_line
 from telemetry.internal.util import path
 from telemetry.internal.util import path_set
+from telemetry.util import classes_util
+
 
 DEPS_FILE = 'bootstrap_deps'
 
@@ -62,10 +63,9 @@ def FindPageSetDependencies(base_dir):
 
   # Add base_dir to path so our imports relative to base_dir will work.
   sys.path.append(base_dir)
-  tests = discover.DiscoverClasses(base_dir, base_dir, benchmark.Benchmark,
-                                   index_by_class_name=True)
+  tests = classes_util.DiscoverClasses(base_dir, base_dir, benchmark.Benchmark)
 
-  for test_class in tests.itervalues():
+  for test_class in tests:
     test_obj = test_class()
 
     # Ensure the test's default options are set if needed.