Remove existing FrameNavigationEntry when new named frame is added.

content/browser/frame_host/navigation_entry_impl.h

Index: content/browser/frame_host/navigation_entry_impl.h
diff --git a/content/browser/frame_host/navigation_entry_impl.h b/content/browser/frame_host/navigation_entry_impl.h
index 83aed388371c8eab32b04c55dd33b3922bcf861e..e76f391ad6cceff250cf72f4c7f2e3ccc6d2675b 100644
--- a/content/browser/frame_host/navigation_entry_impl.h
+++ b/content/browser/frame_host/navigation_entry_impl.h
@@ -232,6 +232,12 @@ class CONTENT_EXPORT NavigationEntryImpl
   // during session history navigations, when the child items no longer apply.
   void ClearChildren(FrameTreeNode* frame_tree_node);
 
+  // Removes any subframe FrameNavigationEntries that match the unique name of
+  // |frame_tree_node|, and all of their children. There should be at most one,
+  // since collisions are avoided but leave old FrameNavigationEntries in the
+  // tree after their frame has been detached.
+  void ClearStaleFrameEntriesForNewFrame(FrameTreeNode* frame_tree_node);
+
   void set_unique_id(int unique_id) {
     unique_id_ = unique_id;
   }