Add loading mobile story set

tools/perf/benchmarks/loading.py

+# Copyright 2016 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.
+
+import page_sets
+
+from benchmarks import page_cycler_v2
+from telemetry.page import cache_temperature
+
+
+class LoadingMobile(page_cycler_v2.PageCyclerV2):
+  """ A benchmark measuring loading performance of mobile sites. """
+
+  @classmethod
+  def Name(cls):
+    return 'loading.mobile'
+
+  def CreateStorySet(self, options):
+    return page_sets.LoadingMobileStorySet(cache_temperatures=[
+          cache_temperature.PCV1_COLD, cache_temperature.PCV1_WARM])