Add a broken page to dummy_benchmark.noisy_benchmark_1

*PERF SHERRIF: this CL intentionally breaks dummy_benchmark.noisy_benchmark_1
for intergration testing purpose.

BUG=646628
NOTRY=true

Review-Url: https://codereview.chromium.org/2334323003
Cr-Commit-Position: refs/heads/master@{#418971}

tools/perf/benchmarks/dummy_benchmark.py

@@ -59,3 +59,10 @@ class DummyBenchmarkTwo(_DummyBenchmark):
   @classmethod
   def Name(cls):
     return 'dummy_benchmark.noisy_benchmark_1'
+
+  def CreateStorySet(self, options):
+    del options  # unused
+    story_set = dummy_story_set.DummyStorySet()
+    story_set.AddStory(dummy_story_set.BrokenDummyPage(story_set))
+    return story_set
+