Telemetry media_measurement plus play action and tests.

tools/telemetry/telemetry/page/actions/play.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 performs the "play" action on media elements.
+
+Media elements can be specified by a selector attribute. If no selector is
+defined then then the action attempts to play the first video element or audio
+element on the page. A selector can also be 'all' to play all media elements.
+
+Other attributes to use are: wait_for_playing and wait_for_ended, which forces
+the action to wait untill playing and ended events get fired respectively.
+"""
+
+import os
+
+from telemetry.core import exceptions
+from telemetry.core import util
+from telemetry.page.actions import page_action
+
+
+class PlayAction(page_action.PageAction):
+  def __init__(self, attributes=None):
+    super(PlayAction, self).__init__(attributes)
+
+  def WillRunAction(self, page, tab):
+    """Load the media metrics JS code prior to running the action."""
+    deps_found = tab.EvaluateJavaScript('window.__mediaRecorders != undefined')
+    if not  deps_found:

[scherkus (not reviewing), 2013/06/14 20:50:45]

extra space after not

[shadi, 2013/06/17 19:13:59]

Done.

Nice catch, gpylint did not catch it.

+      with open(
+          # TODO(shadi): Find or define a global path to src/tools in Telemetry.
+          os.path.join(os.path.dirname(__file__), '..', '..', '..', '..',
+                       'perf', 'perf_tools', 'media_metrics.js')) as f:
+        js = f.read()
+        tab.ExecuteJavaScript(js)
+
+  def RunAction(self, page, tab, previous_action):
+    try:
+      selector = self.selector if hasattr(self, 'selector') else ''
+      tab.ExecuteJavaScript('window.__playMedia(\'%s\');' % selector)
+      # Check if we need to wait for 'playing' event to fire.
+      if hasattr(self, 'wait_for_playing') and self.wait_for_playing:
+        self.WaitForEvent(tab, selector, 'playing')
+      # Check if we need to wait for 'ended' event to fire.
+      if hasattr(self, 'wait_for_ended') and self.wait_for_ended:
+        self.WaitForEvent(tab, selector, 'ended')
+    except exceptions.EvaluateException:
+      raise page_action.PageActionFailed('Cannot play media element(s) with '
+                                         'selector = %s.' % selector)
+
+  def WaitForEvent(self, tab, selector, event_name):
+    """Halts play action untill the selector's event is fired."""

[scherkus (not reviewing), 2013/06/14 20:50:45]

s/untill/until/

[shadi, 2013/06/17 19:13:59]

Done.

+    # TODO(shadi): add action attribute to control timeout for videos that take
+    # longer than 60 secs to end.
+    util.WaitFor(lambda: self.HasEventCompleted(tab, selector, event_name),
+                 timeout=60, poll_interval=0.5)
+
+  def HasEventCompleted(self, tab, selector, event_name):
+    return tab.EvaluateJavaScript(
+        'window.__hasEventCompleted(\'%s\', \'%s\');' % (selector, event_name))