Remove existing FrameNavigationEntry when new named frame is added.

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index e3d331ac9f722a1b83e5acdd993ec16c0d8454d0..7172711ed81c8a2a9842d3f4d207aa622e39c99d 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -4548,6 +4548,7 @@ void WebContentsImpl::UpdateStateForFrame(RenderFrameHost* render_frame_host,
           frame_entry->document_sequence_number() ||
       exploded_state.top.item_sequence_number !=
           frame_entry->item_sequence_number()) {
+    NOTREACHED();
     return;
   }