Notify the renderer if a history navigation has no subframe items.

content/browser/frame_host/navigation_request.cc

 // 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.
 
 #include "content/browser/frame_host/navigation_request.h"
 
 #include <utility>
 
 #include "content/browser/devtools/render_frame_devtools_agent_host.h"
 #include "content/browser/frame_host/frame_tree.h"
@@ skipping 86 matching lines @@
       frame_tree_node, entry.ConstructCommonNavigationParams(
                            frame_entry, request_body, dest_url, dest_referrer,
                            navigation_type, lofi_state, navigation_start),
       BeginNavigationParams(headers.ToString(), net::LOAD_NORMAL,
                             false,  // has_user_gestures
                             false,  // skip_service_worker
                             REQUEST_CONTEXT_TYPE_LOCATION),
       entry.ConstructRequestNavigationParams(
           frame_entry, is_same_document_history_load,
           is_history_navigation_in_new_child,
+          entry.HasSubtreeHistoryItems(frame_tree_node),
           frame_tree_node->has_committed_real_load(),
           controller->GetPendingEntryIndex() == -1,
           controller->GetIndexOfEntry(&entry),
           controller->GetLastCommittedEntryIndex(),
           controller->GetEntryCount()),
       true, &frame_entry, &entry));
   return navigation_request;
 }
 
 // static
@@ skipping 12 matching lines @@
   RequestNavigationParams request_params(
       false,                   // is_overriding_user_agent
       std::vector<GURL>(),     // redirects
       false,                   // can_load_local_resources
       base::Time::Now(),       // request_time
       PageState(),             // page_state
       -1,                      // page_id
       0,                       // nav_entry_id
       false,                   // is_same_document_history_load
       false,                   // is_history_navigation_in_new_child
+      false,                   // has_subtree_history_items

[alexmos, 2016/09/22 01:44:06]

Just for my own understanding: why can we assume this is always false?  Would
something like history.back() be treated as a browser-initiated navigation? 

[Charlie Reis, 2016/09/22 21:00:37]

Good question, and yes.  Renderer-initiated history navigations get punted to
the browser process via a GoToEntryAtOffset IPC message, which then goes through
the browser-initiated back/forward path.  (In some sense, it's not great that a
renderer can cause a "browser initiated" navigation, but it's only to an entry
the user has already been to.)

Just to be sure, I tried it in --enable-browser-side-navigation and verified
that history.back() goes through NavigationRequest::CreateBrowserInitiated, not
here.

       frame_tree_node->has_committed_real_load(),
       false,                   // intended_as_new_entry
       -1,                      // pending_history_list_offset
       current_history_list_offset, current_history_list_length,
       false,                   // is_view_source
       false);                  // should_clear_history_list
   std::unique_ptr<NavigationRequest> navigation_request(
       new NavigationRequest(frame_tree_node, common_params, begin_params,
                             request_params, false, nullptr, nullptr));
   return navigation_request;
@@ skipping 322 matching lines @@
 
   TransferNavigationHandleOwnership(render_frame_host);
   render_frame_host->CommitNavigation(response_.get(), std::move(body_),
                                       common_params_, request_params_,
                                       is_view_source_);
 
   frame_tree_node_->ResetNavigationRequest(true);
 }
 
 }  // namespace content