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

tools/perf/benchmarks/gpu_times.py

 # Copyright 2015 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.
 from benchmarks import silk_flags
 import page_sets
 from telemetry import benchmark
 from telemetry.core.platform import tracing_category_filter
 from telemetry.web_perf import timeline_based_measurement
 from telemetry.web_perf.metrics import gpu_timeline
 
 TOPLEVEL_GL_CATEGORY = 'gpu_toplevel'
 TOPLEVEL_CATEGORIES = ['disabled-by-default-gpu.device',
                        'disabled-by-default-gpu.service']
 
 
 def _GetGPUTimelineMetric(_):
       return [gpu_timeline.GPUTimelineMetric()]
 
 
 class _GPUTimes(benchmark.Benchmark):
   def CreateTimelineBasedMeasurementOptions(self):
     cat_string = ','.join(TOPLEVEL_CATEGORIES)
     cat_filter = tracing_category_filter.TracingCategoryFilter(cat_string)
 
     return timeline_based_measurement.Options(
         overhead_level=cat_filter,
         get_metrics_from_flags_callback=_GetGPUTimelineMetric)
 
   @classmethod
-  def ValueCanBeAddedPredicate(cls, value):
+  def ValueCanBeAddedPredicate(cls, value, _):
     return (isinstance(value, gpu_timeline.GPUTimelineListOfValues) or
             isinstance(value, gpu_timeline.GPUTimelineValue))
 
 @benchmark.Disabled  # http://crbug.com/455292
 class GPUTimesKeyMobileSites(_GPUTimes):
   """Measures GPU timeline metric on key mobile sites."""
   page_set = page_sets.KeyMobileSitesSmoothPageSet
 
   @classmethod
   def Name(cls):
@@ skipping 25 matching lines @@
   """Measures GPU timeline metric for the top 25 sites with GPU rasterization.
   """
   page_set = page_sets.Top25SmoothPageSet
   def CustomizeBrowserOptions(self, options):
     silk_flags.CustomizeBrowserOptionsForGpuRasterization(options)
 
   @classmethod
   def Name(cls):
     return 'gpu_times.gpu_rasterization.top_25_smooth'