[Telemetry] Add an example for adding an end to end Telemetry benchmark

tools/telemetry/examples/benchmarks/v8_benchmark.py

+# Copyright 2015 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.
+from telemetry import benchmark
+from telemetry.timeline import tracing_category_filter
+from telemetry.web_perf import timeline_based_measurement
+
+from benchmarks import simple_story_set
+from benchmarks import v8_metric
+
+
+class MessageLoopBenchmark(benchmark.Benchmark):
+
+  def CreateStorySet(self, options):
+    return simple_story_set.SimpleStorySet()
+
+  def CreateTimelineBasedMeasurementOptions(self):
+    cat_filter = tracing_category_filter.CreateNoOverheadFilter()
+    # blink.console category is required to make sure that Chrome can output
+    # interaction records in its tracing data.
+    cat_filter.AddIncludedCategory('blink.console')
+    cat_filter.AddIncludedCategory('v8')
+    options = timeline_based_measurement.Options(overhead_level=cat_filter)
+    options.SetTimelineBasedMetrics(
+        [v8_metric.MessageLoopLatencyMetric()])
+    return options
+
+  @classmethod
+  def Name(cls):
+    return 'v8_latency.simple_story'