Add background stories to MobileSystemHealth

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 273 matching lines @@
   def _Login(self, action_runner):
     google_login.LoginGoogleAccount(action_runner, 'googletest',
                                     self.credentials_path)
 
     # Navigating to https://mail.google.com immediately leads to an infinite
     # redirection loop due to a bug in WPR (see
     # https://github.com/chromium/web-page-replay/issues/70). We therefore first
     # navigate to a sub-URL to set up the session and hit the resulting
     # redirection loop. Afterwards, we can safely navigate to
     # https://mail.google.com.
+    action_runner.tab.WaitForDocumentReadyStateToBeComplete()

[perezju, 2016/10/06 13:32:42]

why do we need this now?

[hjd, 2016/10/06 15:27:35]

Otherwise we never end up seeing the Navigate below.
I'm not entirely sure why, it feels like we try to navigate before the page is
done loading or something and then the navigate gets lost.
I think it is caused by something on the page changing (the original Gmail story
no longer works with --use-live-sites).

[perezju, 2016/10/06 15:32:54]

Ok, sounds good. Maybe just double-check after recording that both the original
and the new story work.

     action_runner.Navigate(
         'https://mail.google.com/mail/mu/mp/872/trigger_redirection_loop')
     action_runner.tab.WaitForDocumentReadyStateToBeComplete()
 
 
 class LoadGmailDesktopStory(_LoadGmailBaseStory):
   SUPPORTED_PLATFORMS = platforms.DESKTOP_ONLY
 
   def _DidLoadDocument(self, action_runner):
     # Wait until the UI loads.
@@ skipping 85 matching lines @@
   NAME = 'load:games:miniclip'
   # Using "https://" causes "404 Not Found" during WPR recording.
   URL = 'http://www.miniclip.com/games/en/'
   SUPPORTED_PLATFORMS = platforms.DESKTOP_ONLY  # Requires Flash.
 
 
 class LoadAlphabettyStory(_LoadingStory):
   NAME = 'load:games:alphabetty'
   URL = 'https://king.com/play/alphabetty'
   SUPPORTED_PLATFORMS = platforms.DESKTOP_ONLY  # Requires Flash.