Add Telemetry media loop action.

tools/telemetry/telemetry/page/actions/media_action.py

 # Copyright 2013 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.
 
 """Common media action functions."""
 
 import os
 
 from telemetry.core import util
 from telemetry.page.actions import page_action
 
 
 class MediaAction(page_action.PageAction):
-  def __init__(self, attributes=None):
-    super(MediaAction, self).__init__(attributes)
-
   def WillRunAction(self, page, tab):
     """Loads the common media action JS code prior to running the action."""
     self.LoadJS(tab, 'media_action.js')
 
   def RunAction(self, page, tab, previous_action):
     super(MediaAction, self).RunAction(page, tab, previous_action)
 
   def LoadJS(self, tab, js_file_name):
     """Loads and executes a JS file in the tab."""
     with open(os.path.join(os.path.dirname(__file__), js_file_name)) as f:
@@ skipping 10 matching lines @@
       event_name: Name of the event to check if fired or not.
       timeout: Timeout to check for event, throws an exception if not fired.
       poll_interval: Interval to poll for event firing status.
     """
     util.WaitFor(lambda: self.HasEventCompleted(tab, selector, event_name),
                  timeout=timeout, poll_interval=poll_interval)
 
   def HasEventCompleted(self, tab, selector, event_name):
     return tab.EvaluateJavaScript(
         'window.__hasEventCompleted("%s", "%s");' % (selector, event_name))