Use the Previews Black List for server previews

chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/loader/chrome_resource_dispatcher_host_delegate.h"
 
 #include <stdint.h>
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 874 matching lines @@
 content::PreviewsState ChromeResourceDispatcherHostDelegate::GetPreviewsState(
     const net::URLRequest& url_request,
     content::ResourceContext* resource_context) {
   ProfileIOData* io_data = ProfileIOData::FromResourceContext(resource_context);
   data_reduction_proxy::DataReductionProxyIOData* data_reduction_proxy_io_data =
       io_data->data_reduction_proxy_io_data();
 
   content::PreviewsState previews_state = content::PREVIEWS_UNSPECIFIED;
 
   if (data_reduction_proxy_io_data) {
-    if (data_reduction_proxy_io_data->ShouldEnableLoFi(url_request))
+    previews::PreviewsIOData* previews_io_data = io_data->previews_io_data();

[megjablon, 2017/05/10 19:11:23]

Should there be a null check here? Can we move this line above and do: 

if (data_reduction_proxy_io_data && previews_io_data)

and remove the previews_io_data check in the if statement on 907.

[RyanSturm, 2017/05/10 19:57:02]

Done.

+    if (data_reduction_proxy_io_data->ShouldEnableLoFi(url_request,
+                                                       previews_io_data))
       previews_state |= content::SERVER_LOFI_ON;
-    if (data_reduction_proxy_io_data->ShouldEnableLitePages(url_request))
+    if (data_reduction_proxy_io_data->ShouldEnableLitePages(url_request,
+                                                            previews_io_data))
       previews_state |= content::SERVER_LITE_PAGE_ON;
 
-    previews::PreviewsIOData* previews_io_data = io_data->previews_io_data();
     // Check that data saver is enabled, the user isn't opted out of LoFi for
     // the session, and the user is eligible for previews.
     if (data_reduction_proxy_io_data->IsEnabled() &&
         !data_reduction_proxy_io_data->config()->lofi_off() &&
         previews_io_data && previews::params::IsClientLoFiEnabled() &&
         previews_io_data->ShouldAllowPreviewAtECT(
             url_request, previews::PreviewsType::LOFI,
             previews::params::
                 EffectiveConnectionTypeThresholdForClientLoFi())) {
       previews_state |= content::CLIENT_LOFI_ON;
@@ skipping 50 matching lines @@
             &ChromeResourceDispatcherHostDelegate::OnAbortedFrameLoad,
             base::Unretained(this), url, request_loading_time));
     return;
   }
 
   std::string metric_name = (request_loading_time.InMilliseconds() < 100 ?
       "Net.ErrAborted.Fast" : "Net.ErrAborted.Slow");
   rappor::SampleDomainAndRegistryFromGURL(
       g_browser_process->rappor_service(), metric_name, url);
 }