Task Execution Duration metrics added as a new benchmark

tools/perf/page_sets/key_mobile_sites.py

Index: tools/perf/page_sets/key_mobile_sites.py
diff --git a/tools/perf/page_sets/key_mobile_sites.py b/tools/perf/page_sets/key_mobile_sites.py
index 2f058fc3331f47c479b6b19632b6959cfd8b2695..2f1e16cc563d62a5b49c8180ae3a99fe449e6da1 100644
--- a/tools/perf/page_sets/key_mobile_sites.py
+++ b/tools/perf/page_sets/key_mobile_sites.py
@@ -10,7 +10,7 @@ class KeyMobileSitesPage(page_module.Page):
   def __init__(self, url, page_set, name=''):
     super(KeyMobileSitesPage, self).__init__(
         url=url, page_set=page_set, name=name,
-        credentials_path = 'data/credentials.json')
+        credentials_path='data/credentials.json')
     self.user_agent_type = 'mobile'
     self.archive_data_file = 'data/key_mobile_sites.json'
 
@@ -23,6 +23,12 @@ class KeyMobileSitesPage(page_module.Page):
   def RunRepaint(self, action_runner):
     action_runner.RepaintContinuously(seconds=5)
 
+  def RunTaskExecutionTime(self, action_runner):
+    interaction = action_runner.BeginGestureInteraction(
+        'ScrollAction', is_smooth=True)
+    action_runner.ScrollPage()
+    interaction.End()
+
 
 class Page1(KeyMobileSitesPage):