Implement a more stable way to check if the dialog is fully loaded before choose the sink, instead …

chrome/test/media_router/telemetry/benchmarks/pagesets/media_router_page.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 logging
 import os
 import time
 import utils
 
 from telemetry import page
@@ skipping 73 matching lines @@
     return route
 
   def ExecuteAsyncJavaScript(self, action_runner, script, verify_func,
                              error_message, timeout=5):
     """Executes async javascript function and waits until it finishes."""
 
     action_runner.ExecuteJavaScript(script)
     self._WaitForResult(action_runner, verify_func, error_message,
                         timeout=timeout)
 
+  def WaitUntilDialogLoaded(self, action_runner, tab):
+    """Waits until dialog is fully loaded."""
+
+    self._WaitForResult(
+        action_runner,
+        lambda: tab.EvaluateJavaScript(
+             '!!window.document.getElementById('
+             '"media-router-container") &&'
+             'window.document.getElementById('
+             '"media-router-container").sinksToShow_ &&'
+             'window.document.getElementById('
+             '"media-router-container").sinksToShow_.length'),
+        'The dialog is not fully loaded within 15s.',
+         timeout=15)
+
   def _WaitForResult(self, action_runner, verify_func, error_message,
                      timeout=5):
     """Waits until the function finishes or timeout."""
 
     start_time = time.time()
     while (not verify_func() and
            time.time() - start_time < timeout):
       action_runner.Wait(1)
     if not verify_func():
       raise page.page_test.Failure(error_message)
 
   def _GetDeviceName(self):
     """Gets device name from environment variable RECEIVER_NAME."""
 
     if 'RECEIVER_IP' not in os.environ or not os.environ.get('RECEIVER_IP'):
       raise page.page_test.Failure(
           'Your test machine is not set up correctly, '
           'RECEIVER_IP enviroment variable is missing.')
     return utils.GetDeviceName(os.environ.get('RECEIVER_IP'))