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

tools/perf/benchmarks/session_restore.py

Index: tools/perf/benchmarks/session_restore.py
diff --git a/tools/perf/benchmarks/session_restore.py b/tools/perf/benchmarks/session_restore.py
index 997b904a046d27d18187c681423c492dbffc62c4..5e8ced524c5cb9b2e2e6a4d6ab5c1188a0f16f8b 100644
--- a/tools/perf/benchmarks/session_restore.py
+++ b/tools/perf/benchmarks/session_restore.py
@@ -23,6 +23,7 @@ class _SessionRestoreTypical25(benchmark.Benchmark):
   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):
@@ -47,6 +48,7 @@ class _SessionRestoreTypical25(benchmark.Benchmark):
         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.