Fix tab_switching measurement bug.

tools/perf/benchmarks/benchmark_smoke_unittest.py

Index: tools/perf/benchmarks/benchmark_smoke_unittest.py
diff --git a/tools/perf/benchmarks/benchmark_smoke_unittest.py b/tools/perf/benchmarks/benchmark_smoke_unittest.py
index 209e658badaa03b38f537c0784883d98da6297db..9925c0f17edd4230dc9e931d0e70ce51c3cc9d8e 100644
--- a/tools/perf/benchmarks/benchmark_smoke_unittest.py
+++ b/tools/perf/benchmarks/benchmark_smoke_unittest.py
@@ -32,7 +32,8 @@ from benchmarks import speedometer
 from benchmarks import jetstream
 
 
-def SmokeTestGenerator(benchmark):
+def SmokeTestGenerator(benchmark, num_pages=1):
+  """Generates a benchmark that includes first N pages from pageset."""
   # NOTE TO SHERIFFS: DO NOT DISABLE THIS TEST.
   #
   # This smoke test dynamically tests all benchmarks. So disabling it for one
@@ -49,10 +50,11 @@ def SmokeTestGenerator(benchmark):
       def CreatePageSet(self, options):
         # pylint: disable=E1002
         ps = super(SinglePageBenchmark, self).CreatePageSet(options)
-        for p in ps.pages:
+        user_stories = []
+        for p in ps.pages[:num_pages]:
           p.skip_waits = True
-          ps.user_stories = [p]
-          break
+          user_stories.append(p)
+        ps.user_stories = user_stories
         return ps
 
     # Set the benchmark's default arguments.
@@ -128,7 +130,11 @@ def load_tests(loader, standard_tests, pattern):
     class BenchmarkSmokeTest(unittest.TestCase):
       pass
 
-    method = SmokeTestGenerator(benchmark)
+    # It is wrong to give tab_switching only one page to switch.
+    if 'tab_switching' in benchmark.Name():
+      method = SmokeTestGenerator(benchmark, num_pages=2)

[nednguyen, 2015/06/24 14:53:10]

This fix is reasonable. But please check the cycle time of
telemetry_perf_unittest in mac_chromium_rel_ng, win_chromium_rel_ng,
win_chromium_x64_rel_ng, linux_android_rel_ng to make sure that they don't
exceed 3 minutes.

+    else:
+      method = SmokeTestGenerator(benchmark)
 
     # Make sure any decorators are propagated from the original declaration.
     # (access to protected members) pylint: disable=W0212