Prefetch all WPR archives used by system_health_smoke_test

tools/perf/benchmarks/system_health_smoke_test.py

 # Copyright 2016 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.
 
 """Run all system health stories used by system health benchmarks.
 
 Only memory benchmarks are used when running these stories to make the total
 cycle time manageable. Other system health benchmarks should be using the same
 stories as memory ones, only with fewer actions (no memory dumping).
 """
@@ skipping 135 matching lines @@
   benchmark_classes = GetSystemHealthBenchmarksToSmokeTest()
   assert benchmark_classes, 'This list should never be empty'
   for benchmark_class in benchmark_classes:
 
     # HACK: these options should be derived from options_for_unittests which are
     # the resolved options from run_tests' arguments. However, options is only
     # parsed during test time which happens after load_tests are called.
     # Since none of our system health benchmarks creates stories based on
     # command line options, it should be ok to pass options=None to
     # CreateStorySet.
-    for story_to_smoke_test in (
-        benchmark_class().CreateStorySet(options=None).stories):
+    stories_set = benchmark_class().CreateStorySet(options=None)
+
+    # Prefetch WPR archive needed by the stories set to avoid race condition
+    # when feching them when tests are run in parallel.
+    # See crbug.com/700426 for more details.
+    stories_set.wpr_archive_info.DownloadArchivesIfNeeded()
+
+    for story_to_smoke_test in stories_set.stories:
       suite.addTest(
           _GenerateSmokeTestCase(benchmark_class, story_to_smoke_test))
 
   return suite