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

tools/telemetry/telemetry/core/platform.py

 # Copyright 2012 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 as real_logging
 import os
 
+from telemetry.core import discover
 from telemetry.core import network_controller
 from telemetry.core import tracing_controller
 from telemetry.core import util
 from telemetry.internal.platform import platform_backend as platform_backend_module
-from telemetry.util import classes_util
 
 
 _host_platform = None
 # Remote platform is a dictionary from device ids to remote platform instances.
 _remote_platforms = {}
 
 
 def _InitHostPlatformIfNeeded():
   global _host_platform
   if _host_platform:
@@ skipping 10 matching lines @@
 
 
 def GetHostPlatform():
   _InitHostPlatformIfNeeded()
   return _host_platform
 
 
 def _IterAllPlatformBackendClasses():
   platform_dir = os.path.dirname(
       os.path.realpath(platform_backend_module.__file__))
-  return classes_util.DiscoverClasses(
+  return discover.DiscoverClasses(
       platform_dir, util.GetTelemetryDir(),
-      platform_backend_module.PlatformBackend)
+      platform_backend_module.PlatformBackend).itervalues()
 
 
 def GetPlatformForDevice(device, finder_options, logging=real_logging):
   """ Returns a platform instance for the device.
     Args:
       device: a device.Device instance.
   """
   if device.guid in _remote_platforms:
     return _remote_platforms[device.guid]
   try:
@@ skipping 254 matching lines @@
 
     Args:
       proc: a process object returned from subprocess.Popen.
       app_name: on Windows, is the prefix of the application's window
           class name that should be searched for. This helps ensure
           that only the application's windows are closed.
 
     Returns True if it is believed the attempt succeeded.
     """
     return self._platform_backend.CooperativelyShutdown(proc, app_name)