On the Win 10 Perf bot (https://build.chromium.org/p/chromium.perf/builders/Win%2010%20Perf) all of the disabled tests are red. They're failing with a python error; it looks like results_merger.py needs to handle shard_results_list == [].

Traceback (most recent call last):
  File "E:\b\rr\tmplg9fqd\rw\checkout\scripts/slave\recipe_modules\swarming\resources\standard_isolated_script_merge.py", line 45, in <module>
    sys.exit(main())
  File "E:\b\rr\tmplg9fqd\rw\checkout\scripts/slave\recipe_modules\swarming\resources\standard_isolated_script_merge.py", line 41, in main
    return StandardIsolatedScriptMerge(args.output_json, args.jsons_to_merge)
  File "E:\b\rr\tmplg9fqd\rw\checkout\scripts/slave\recipe_modules\swarming\resources\standard_isolated_script_merge.py", line 25, in StandardIsolatedScriptMerge
    merged_results = results_merger.merge_test_results(shard_results_list)
  File "E:\b\rr\tmplg9fqd\rw\checkout\scripts\slave\recipe_modules\swarming\resources\results_merger.py", line 64, in merge_test_results
    if 'seconds_since_epoch' in shard_results_list[0]:
TypeError: argument of type 'NoneType' is not iterable