Tell renderer which subframes have history items on back/forward.

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 07714ab620792d4c19857e810f604a41dadf1fb1..e48b529edadcadb9756a11f01ffce99438bb643e 100644
--- a/content/browser/frame_host/navigation_request.cc
+++ b/content/browser/frame_host/navigation_request.cc
@@ -100,7 +100,7 @@ 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),
+          entry.GetSubframeUniqueNames(frame_tree_node),
           frame_tree_node->has_committed_real_load(),
           controller->GetPendingEntryIndex() == -1,
           controller->GetIndexOfEntry(&entry),
@@ -133,7 +133,7 @@ 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
+      std::set<std::string>(), // subframe_unique_names
       frame_tree_node->has_committed_real_load(),
       false,                   // intended_as_new_entry
       -1,                      // pending_history_list_offset