[system health] Make mobile washington post story more robust.

tools/perf/page_sets/system_health/loading_stories.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.
 
 from page_sets.system_health import platforms
 from page_sets.system_health import system_health_story
 
 from page_sets.login_helpers import dropbox_login
 from page_sets.login_helpers import google_login
 
@@ skipping 160 matching lines @@
   # always fails to completely load due to
   # https://github.com/chromium/web-page-replay/issues/74.
   SUPPORTED_PLATFORMS = platforms.MOBILE_ONLY
 
 
 class LoadWashingtonPostMobileStory(_LoadingStory):
   NAME = 'load:news:washingtonpost'
   URL = 'https://www.washingtonpost.com/pwa'
   SUPPORTED_PLATFORMS = platforms.MOBILE_ONLY
   _CLOSE_BUTTON_SELECTOR = '.close'
+  _MAIL_BUTTON_SELECTOR = '.mailBlock'
 
   def _DidLoadDocument(self, action_runner):
     # Close the popup window. On Nexus 9 (and probably other tables) the popup
     # window does not have a "Close" button, instead it has only a "Send link
     # to phone" button. So on tablets we run with the popup window open. The
     # popup is transparent, so this is mostly an aesthetical issue.
-    has_button = action_runner.EvaluateJavaScript(
+    action_runner.WaitForElement(selector="%s, %s" %
+        (self._CLOSE_BUTTON_SELECTOR, self._MAIL_BUTTON_SELECTOR))
+    has_close_button = action_runner.EvaluateJavaScript(
         '!!document.querySelector("%s")' % self._CLOSE_BUTTON_SELECTOR)
-    if has_button:
+    if has_close_button:
       action_runner.ClickElement(selector=self._CLOSE_BUTTON_SELECTOR)
 
 
 class LoadWikipediaStory(_LoadingStory):
   NAME = 'load:news:wikipedia'
   URL = 'https://en.wikipedia.org/wiki/Science'
 
 
 ################################################################################
 # Audio and video.
@@ skipping 169 matching lines @@
   URL = 'http://www.miniclip.com/games/en/'
   # Desktop only (requires Flash).
   SUPPORTED_PLATFORMS = platforms.DESKTOP_ONLY
 
 
 class LoadAlphabettyStory(_LoadingStory):
   NAME = 'load:games:alphabetty'
   URL = 'https://king.com/play/alphabetty'
   # Desktop only (requires Flash).
   SUPPORTED_PLATFORMS = platforms.DESKTOP_ONLY