Update benchmark_smoke_test to set the enable_smoke_test flag

Bug: 840427
Change-Id: I80c13fefb4e5594ad29a6511845415584d7ea11a
Reviewed-on: https://chromium-review.googlesource.com/1047854Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Emily Hanley <eyaich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558352}

tools/perf/benchmarks/benchmark_smoke_unittest.py

@@ -51,7 +51,7 @@ def SmokeTestGenerator(benchmark, num_pages=1):
   @decorators.Disabled('android')  # crbug.com/641934
   def BenchmarkSmokeTest(self):
     # Only measure a single page so that this test cycles reasonably quickly.
-    benchmark.options['pageset_repeat'] = 1
+    benchmark.options['smoke_test_mode'] = True
 
     # Some benchmarks are running multiple iterations
     # which is not needed for a smoke test