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

content/renderer/render_frame_impl.cc

 // Copyright 2013 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 "content/renderer/render_frame_impl.h"
 
 #include <map>
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 3582 matching lines @@
           "SessionRestore.SubFrameUniqueNameChangedBeforeFirstCommit",
           name_changed_before_first_commit_);
     }
     committed_first_load_ = true;
   }
 
   DocumentState* document_state =
       DocumentState::FromDataSource(frame->dataSource());
   NavigationStateImpl* navigation_state =
       static_cast<NavigationStateImpl*>(document_state->navigation_state());
+  const WebURLResponse& web_url_response = frame->dataSource()->response();
   WebURLResponseExtraDataImpl* extra_data =
-      GetExtraDataFromResponse(frame->dataSource()->response());
+      GetExtraDataFromResponse(web_url_response);
   // Only update the PreviewsState and effective connection type states for new
   // main frame documents. Subframes inherit from the main frame and should not
   // change at commit time.
   if (is_main_frame_ && !navigation_state->WasWithinSamePage()) {
     previews_state_ =
         extra_data ? extra_data->previews_state() : PREVIEWS_OFF;
+
+    // Set lite pages off if a lite page was not loaded for the main frame.
+    if (web_url_response
+            .httpHeaderField(
+                WebString::fromUTF8("chrome-proxy-content-transform"))

[nasko, 2017/02/16 18:10:02]

Please define a string constant with a symbolic name and use that.

[megjablon, 2017/02/17 20:17:52]

Done.

+            .utf8() != "lite-page") {
+      previews_state_ &= ~(SERVER_LITE_PAGE_ON);
+    }
+
     if (extra_data) {
       effective_connection_type_ =
           EffectiveConnectionTypeToWebEffectiveConnectionType(
               extra_data->effective_connection_type());
     }
   }
 
   if (proxy_routing_id_ != MSG_ROUTING_NONE) {
     // If this is a provisional frame associated with a proxy (i.e., a frame
     // created for a remote-to-local navigation), swap it into the frame tree
@@ skipping 3193 matching lines @@
   // event target. Potentially a Pepper plugin will receive the event.
   // In order to tell whether a plugin gets the last mouse event and which it
   // is, we set |pepper_last_mouse_event_target_| to null here. If a plugin gets
   // the event, it will notify us via DidReceiveMouseEvent() and set itself as
   // |pepper_last_mouse_event_target_|.
   pepper_last_mouse_event_target_ = nullptr;
 #endif
 }
 
 }  // namespace content