Add a new benchmark for cpu power measurements on steady state sites.

tools/perf/benchmarks/power.py

Index: tools/perf/benchmarks/power.py
diff --git a/tools/perf/benchmarks/power.py b/tools/perf/benchmarks/power.py
index e1632e57de12a34225cf8015df80bd82143365c7..1d84778b1a01546ed5a3a4c42cefcc69284e8c59 100644
--- a/tools/perf/benchmarks/power.py
+++ b/tools/perf/benchmarks/power.py
@@ -190,3 +190,14 @@ class PowerScrollingTrivialPage(perf_benchmark.PerfBenchmark):
   @classmethod
   def Name(cls):
     return 'power.trivial_pages'
+
+@benchmark.Enabled('mac')
+class PowerSteadyStatePages(perf_benchmark.PerfBenchmark):
+  """Measure power consumption for real web sites in steady state (no user
+  interactions)."""
+  test = power.QuiescentPower
+  page_set = page_sets.IdleAfterLoadingStories
+
+  @classmethod
+  def Name(cls):
+    return 'power.steady_state'