[Telemetry] Make "discard_first_result" apply to user_stories too.

tools/perf/benchmarks/session_restore.py

 # Copyright 2013 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 os
 import tempfile
 
 from measurements import session_restore
 import page_sets
 from profile_creators import small_profile_creator
 from telemetry import benchmark
 from telemetry.page import profile_generator
 
 
 class _SessionRestoreTypical25(benchmark.Benchmark):
   """Base Benchmark class for session restore benchmarks.
 
   A cold start means none of the Chromium files are in the disk cache.
   A warm start assumes the OS has already cached much of Chromium's content.
   For warm tests, you should repeat the page set to ensure it's cached.
 
   Use Typical25PageSet to match what the SmallProfileCreator uses.
   TODO(slamm): Make SmallProfileCreator and this use the same page_set ref.
   """
   page_set = page_sets.Typical25PageSet
+  tag = None  # subclasses set as 'warm' or 'cold'
 
   @classmethod
   def Name(cls):
     return 'session_restore'
 
   @classmethod
   def ProcessCommandLineArgs(cls, parser, args):
     super(_SessionRestoreTypical25, cls).ProcessCommandLineArgs(parser, args)
     profile_type = 'small_profile'
     if not args.browser_options.profile_dir:
       output_dir = os.path.join(tempfile.gettempdir(), profile_type)
       profile_dir = os.path.join(output_dir, profile_type)
       if not os.path.exists(output_dir):
         os.makedirs(output_dir)
 
       # Generate new profiles if profile_dir does not exist. It only exists if
       # all profiles had been correctly generated in a previous run.
       if not os.path.exists(profile_dir):
         new_args = args.Copy()
         new_args.pageset_repeat = 1
         new_args.output_dir = output_dir
         profile_generator.GenerateProfiles(
             small_profile_creator.SmallProfileCreator, profile_type, new_args)
       args.browser_options.profile_dir = profile_dir
+    args.discard_first_result = cls.tag == 'warm'
 
   def CreateUserStorySet(self, _):
     """Return a user story set that only has the first user story.
 
     The session restore measurement skips the navigation step and
     only tests session restore by having the browser start-up.
     The first user story is used to get WPR set up and hold results.
     """
     user_story_set = self.page_set()
     for user_story in user_story_set.user_stories[1:]:
@@ skipping 26 matching lines @@
 
   The first result is discarded.
   """
   tag = 'warm'
   options = {'pageset_repeat': 20}
 
   @classmethod
   def Name(cls):
     return 'session_restore.warm.typical_25'