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

content/browser/frame_host/navigation_request.cc

Index: content/browser/frame_host/navigation_request.cc
diff --git a/content/browser/frame_host/navigation_request.cc b/content/browser/frame_host/navigation_request.cc
index 3d5d5a12d3dc0b0767ba896ac550628a0a2f634b..f42bd31828af3c0ae3c35857523879a3fafbe4bb 100644
--- a/content/browser/frame_host/navigation_request.cc
+++ b/content/browser/frame_host/navigation_request.cc
@@ -104,6 +104,7 @@ std::unique_ptr<NavigationRequest> NavigationRequest::CreateBrowserInitiated(
       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),
@@ -136,6 +137,7 @@ std::unique_ptr<NavigationRequest> NavigationRequest::CreateRendererInitiated(
       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