Update perf page_set to use story_set

tools/telemetry/telemetry/benchmark.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 optparse
 
 from catapult_base import cloud_storage
 from telemetry.core import command_line
 from telemetry import decorators
 from telemetry.internal.results import results_options
@@ skipping 232 matching lines @@
     return timeline_based_measurement.TimelineBasedMeasurement(opts)
 
   def CreatePageSet(self, options):  # pylint: disable=unused-argument
     """Get the page set this test will run on.
 
     By default, it will create a page set from the this test's page_set
     attribute. Override to generate a custom page set.
     """
     if not hasattr(self, 'page_set'):
       raise NotImplementedError('This test has no "page_set" attribute.')
-    if not issubclass(self.page_set, page_set.PageSet):
-      raise TypeError('"%s" is not a PageSet.' % self.page_set.__name__)
     return self.page_set()
 
   def CreateStorySet(self, options):
     """Creates the instance of StorySet used to run the benchmark.
 
     Can be overridden by subclasses.
     """
     return self.CreatePageSet(options)
 
   @classmethod
   def CreateExpectations(cls):
     """Get the expectations this test will run with.
 
     By default, it will create an empty expectations set. Override to generate
     custom expectations.
     """
     return test_expectations.TestExpectations()
 
 
 def AddCommandLineArgs(parser):
   story_runner.AddCommandLineArgs(parser)
 
 
 def ProcessCommandLineArgs(parser, args):
   story_runner.ProcessCommandLineArgs(parser, args)