Prefetch all WPR archives used by system_health_smoke_test

tools/perf/benchmarks/system_health_smoke_test.py

Index: tools/perf/benchmarks/system_health_smoke_test.py
diff --git a/tools/perf/benchmarks/system_health_smoke_test.py b/tools/perf/benchmarks/system_health_smoke_test.py
index 5e02ad370da7bca82a6c13a79e15d7d974c1b61f..062497ce17555e4d6674fd9cdc24b0d8dc00a79a 100644
--- a/tools/perf/benchmarks/system_health_smoke_test.py
+++ b/tools/perf/benchmarks/system_health_smoke_test.py
@@ -153,8 +153,14 @@ def load_tests(loader, standard_tests, pattern):
     # 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))