Create a Lite Page bit for previews and fallback to Lo-Fi

components/data_reduction_proxy/content/browser/content_lofi_decider.cc

 // 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.
 
 #include "components/data_reduction_proxy/content/browser/content_lofi_decider.h"
 
 #include <string>
 
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_params.h"
 #include "content/public/browser/resource_request_info.h"
 #include "content/public/common/previews_state.h"
 #include "content/public/common/resource_type.h"
 #include "net/base/load_flags.h"
 #include "net/http/http_request_headers.h"
 #include "net/url_request/url_request.h"
 
 namespace data_reduction_proxy {
 
 ContentLoFiDecider::ContentLoFiDecider() {}
 
 ContentLoFiDecider::~ContentLoFiDecider() {}
 
-bool ContentLoFiDecider::IsUsingLoFiMode(const net::URLRequest& request) const {
+bool ContentLoFiDecider::IsUsingLoFi(const net::URLRequest& request) const {
   const content::ResourceRequestInfo* request_info =
       content::ResourceRequestInfo::ForRequest(&request);
   // The Lo-Fi directive should not be added for users in the Lo-Fi field
   // trial "Control" group. Check that the user is in a group that can get
   // "q=low".
   bool lofi_enabled_via_flag_or_field_trial =
       params::IsLoFiOnViaFlags() || params::IsIncludedInLoFiEnabledFieldTrial();
 
   // Return if the user is using Lo-Fi and not part of the "Control" group.
   if (request_info) {
     return (request_info->GetPreviewsState() & content::SERVER_LOFI_ON) &&
            lofi_enabled_via_flag_or_field_trial;
   }
   return false;
 }
 
 void ContentLoFiDecider::MaybeSetAcceptTransformHeader(
     const net::URLRequest& request,
-    bool is_previews_disabled,
+    bool are_previews_disabled,
     net::HttpRequestHeaders* headers) const {
   const content::ResourceRequestInfo* request_info =
       content::ResourceRequestInfo::ForRequest(&request);
 
   if (!request_info)
     return;
 
   // Previews only operate on HTTP.
   if (!request.url().SchemeIs("http"))
     return;
@@ skipping 19 matching lines @@
       (params::IsLoFiOnViaFlags() && params::AreLitePagesEnabledViaFlags()) ||
       params::IsIncludedInLitePageFieldTrial();
 
   // User does not have previews enabled.
   if (!lofi_enabled_via_flags_or_field_trial &&
       !lite_page_enabled_via_flags_or_field_trial) {
     return;
   }
 
   // Previews has been disabled.
-  if (is_previews_disabled)
+  if (are_previews_disabled)
     return;
 
   // Do not add the Chrome-Proxy-Accept-Transform header when the page load
   // explicitly forbids previews transformations.
   if (request_info->GetPreviewsState() & content::PREVIEWS_NO_TRANSFORM)
     return;
 
-  // LoFi is not allowed on the main frame, stylesheet, script, font resource,
+  // Lo-Fi is not allowed on the main frame, stylesheet, script, font resource,
   // media, service worker, or CSP report.
   bool resource_type_supports_empty_image =
       !(resource_type == content::RESOURCE_TYPE_MAIN_FRAME ||
         resource_type == content::RESOURCE_TYPE_STYLESHEET ||
         resource_type == content::RESOURCE_TYPE_SCRIPT ||
         resource_type == content::RESOURCE_TYPE_FONT_RESOURCE ||
         resource_type == content::RESOURCE_TYPE_MEDIA ||
         resource_type == content::RESOURCE_TYPE_CSP_REPORT);
 
-  // If in the lite page field trial or the lite page flag is enabled, only add
-  // the "lite-page" directive on main frame requests. Do not add "empty-image"
-  // directives to other requests when Lite Page previews are enabled.
-  // Add the "if-heavy" qualifier to allow the server to provide a preview when
-  // the page is data heavy on if a preview was not otherwise triggered.
+  // If the Lite Page field trial or flag is enabled, only add the "lite-page"
+  // directive on main frame requests. Only add "empty-image" directives to
+  // other requests when Lite Page previews are not enabled after the main
+  // frame. Add the "if-heavy" qualifier to allow the server to provide a
+  // preview when the page is data heavy on if a preview was not otherwise
+  // triggered.
   std::string accept_transform_value;
-  if (lite_page_enabled_via_flags_or_field_trial) {
-    if (resource_type == content::RESOURCE_TYPE_MAIN_FRAME)
-      accept_transform_value = lite_page_directive();
-  } else if (lofi_enabled_via_flags_or_field_trial) {
-    if (resource_type_supports_empty_image)
-      accept_transform_value = empty_image_directive();
+  if (lite_page_enabled_via_flags_or_field_trial &&
+      resource_type == content::RESOURCE_TYPE_MAIN_FRAME) {
+    accept_transform_value = lite_page_directive();
+
+    if (!(request_info->GetPreviewsState() & content::SERVER_LITE_PAGE_ON))

[bengr, 2017/02/15 00:03:47]

Add a comment:
// Since a lite page was not triggered client side, ask the server to
// provide a lite page only if the page is otherwise data-heavy.

Add a similar comment before line 123.

[megjablon, 2017/02/16 04:29:09]

Done.

+      accept_transform_value += base::StringPrintf(";%s", if_heavy_qualifier());
+  } else if (lofi_enabled_via_flags_or_field_trial &&
+             resource_type_supports_empty_image &&
+             !(request_info->GetPreviewsState() &
+               content::SERVER_LITE_PAGE_ON)) {
+    accept_transform_value = empty_image_directive();
+
+    if (!(request_info->GetPreviewsState() & content::SERVER_LOFI_ON))
+      accept_transform_value += base::StringPrintf(";%s", if_heavy_qualifier());
   }
   if (accept_transform_value.empty())
     return;
 
-  if (!(request_info->GetPreviewsState() & content::SERVER_LOFI_ON))
-    accept_transform_value += base::StringPrintf(";%s", if_heavy_qualifier());
-
   headers->SetHeader(chrome_proxy_accept_transform_header(),
                      accept_transform_value);
 }
 
 bool ContentLoFiDecider::IsSlowPagePreviewRequested(
     const net::HttpRequestHeaders& headers) const {
   std::string accept_transform_header_value;
   if (!headers.GetHeader(chrome_proxy_accept_transform_header(),
                          &accept_transform_header_value)) {
     return false;
@@ skipping 49 matching lines @@
   headers->SetHeader(chrome_proxy_header(), chrome_proxy_header_value);
 }
 
 bool ContentLoFiDecider::ShouldRecordLoFiUMA(
     const net::URLRequest& request) const {
   const content::ResourceRequestInfo* request_info =
       content::ResourceRequestInfo::ForRequest(&request);
 
   // User is not using Lo-Fi.
   if (!request_info ||
-      !(request_info->GetPreviewsState() & content::SERVER_LOFI_ON)) {
+      !(request_info->GetPreviewsState() & content::SERVER_LOFI_ON ||
+        request_info->GetPreviewsState() & content::SERVER_LITE_PAGE_ON)) {
     return false;
   }
 
   return params::IsIncludedInLoFiEnabledFieldTrial() ||
          params::IsIncludedInLoFiControlFieldTrial();
 }
 
 }  // namespace data_reduction_proxy