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

content/common/navigation_params.h

Index: content/common/navigation_params.h
diff --git a/content/common/navigation_params.h b/content/common/navigation_params.h
index f288a14072dcee89ba203b7056e035cc18b71b63..3ac9b8c6f8ead067c90c81b98e03049bd80c497f 100644
--- a/content/common/navigation_params.h
+++ b/content/common/navigation_params.h
@@ -228,6 +228,7 @@ struct CONTENT_EXPORT RequestNavigationParams {
                           int nav_entry_id,
                           bool is_same_document_history_load,
                           bool is_history_navigation_in_new_child,
+                          bool has_subtree_history_items,
                           bool has_committed_real_load,
                           bool intended_as_new_entry,
                           int pending_history_list_offset,
@@ -278,6 +279,14 @@ struct CONTENT_EXPORT RequestNavigationParams {
   // a URL from a session history item.  Defaults to false.
   bool is_history_navigation_in_new_child;
 
+  // If this is a history navigation, this indicates whether the browser process
+  // is aware of any subframe history items for the given frame.  If not, the
+  // renderer does not need to check with the browser if any subframes are
+  // created during the navigation.
+  // TODO(creis): Expand this to a data structure of unique names and
+  // corresponding PageStates in https://crbug.com/639842.
+  bool has_subtree_history_items;
+
   // Whether the frame being navigated has already committed a real page, which
   // affects how new navigations are classified in the renderer process.
   // This currently is only ever set to true in --site-per-process mode.