Add Telemetry media loop action.

tools/telemetry/telemetry/page/actions/loop.py

+# Copyright (c) 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.
+
+"""A Telemetry page_action that loops media playback.
+
+Action attributes are:
+- loop_count: The number of times to loop media.
+- selector: If no selector is defined then the action attempts to loop the first
+            media element on the page. If 'all' then loop all media elements.
+- wait_timeout: Timeout to wait for media to loop. Default is
+                60 sec x loop_count.
+- wait_for_loop: If true, forces the action to wait for last loop to end,
+                 otherwise it starts the loops and exit. Default true.
+"""
+
+from telemetry.core import exceptions
+from telemetry.page.actions import page_action
+import telemetry.page.actions.media_action as media_action
+
+
+class LoopAction(media_action.MediaAction):
+  def WillRunAction(self, page, tab):
+    """Load the media metrics JS code prior to running the action."""
+    super(LoopAction, self).WillRunAction(page, tab)
+    self.LoadJS(tab, 'loop.js')
+
+  def RunAction(self, page, tab, previous_action):
+    try:
+      assert hasattr(self, 'loop_count') and self.loop_count > 0
+      selector = self.selector if hasattr(self, 'selector') else ''
+      tab.ExecuteJavaScript('window.__loopMedia("%s", %i);' %
+                            (selector, self.loop_count))
+      timeout = (self.wait_timeout if hasattr(self, 'wait_timeout')
+                 else 60 * self.loop_count)
+      # Check if there is no need to wait for all loops to end
+      if hasattr(self, 'wait_for_loop') and not self.wait_for_loop:
+        return
+      self.WaitForEvent(tab, selector, 'loop', timeout)
+    except exceptions.EvaluateException:
+      raise page_action.PageActionFailed('Cannot loop media element(s) with '
+                                         'selector = %s.' % selector)