Use an uncacheable page for the Lo-Fi integration test

tools/chrome_proxy/integration_tests/chrome_proxy_pagesets/lo_fi.py

 # Copyright 2015 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 import story
 
 
 class LoFiPage(page_module.Page):
   """
   A test page for the chrome proxy Lo-Fi tests.
   Checks that the compressed image is below a certain threshold.
+  The test page is uncacheable otherwise a cached page may be served that
+  doesn't have the correct via headers.
   """
 
   def __init__(self, url, page_set):
     super(LoFiPage, self).__init__(url=url, page_set=page_set)
 
 
 class LoFiStorySet(story.StorySet):
   """ Chrome proxy test sites """
 
   def __init__(self):
     super(LoFiStorySet, self).__init__()
 
     urls_list = [
-      'http://check.googlezip.net/cacheable/test.html',
+      'http://check.googlezip.net/static/index.html',
     ]
 
     for url in urls_list:
       self.AddStory(LoFiPage(url, self))