Move top_20 tests to a separate suite

tools/chrome_proxy/integration_tests/pagesets/http_to_direct_fallback.py

 # Copyright 2014 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 telemetry.page import page as page_module
 from telemetry.page import page_set as page_set_module
 
 
 class HTTPToDirectFallbackPage(page_module.Page):
   """Page that tests falling back from the HTTP proxy to a direct connection."""
   def __init__(self, url, page_set):
     super(HTTPToDirectFallbackPage, self).__init__(url=url, page_set=page_set)
 
 
 class HTTPToDirectFallbackPageSet(page_set_module.PageSet):
   """Chrome proxy test sites"""
   def __init__(self):
     super(HTTPToDirectFallbackPageSet, self).__init__()
 
     urls_list = [
       'http://check.googlezip.net/fallback',
       'http://aws1.mdw.la/bypass',
     ]
 
     for url in urls_list:
       self.AddUserStory(HTTPToDirectFallbackPage(url, self))