Remove existing FrameNavigationEntry when new named frame is added.

content/browser/frame_host/frame_tree.cc

Index: content/browser/frame_host/frame_tree.cc
diff --git a/content/browser/frame_host/frame_tree.cc b/content/browser/frame_host/frame_tree.cc
index 300075f79e4e3835c6f63d65447355b5809c4c34..511454f4d1069275dedc0d193778593d0d395985 100644
--- a/content/browser/frame_host/frame_tree.cc
+++ b/content/browser/frame_host/frame_tree.cc
@@ -15,6 +15,8 @@
 #include "base/lazy_instance.h"
 #include "base/memory/ptr_util.h"
 #include "content/browser/frame_host/frame_tree_node.h"
+#include "content/browser/frame_host/navigation_controller_impl.h"
+#include "content/browser/frame_host/navigation_entry_impl.h"
 #include "content/browser/frame_host/navigator.h"
 #include "content/browser/frame_host/render_frame_host_factory.h"
 #include "content/browser/frame_host/render_frame_host_impl.h"
@@ -192,6 +194,15 @@ bool FrameTree::AddFrame(FrameTreeNode* parent,
           frame_unique_name, frame_owner_properties)),
       process_id, new_routing_id);
 
+  // The last committed NavigationEntry may have a FrameNavigationEntry with the
+  // same |frame_unique_name|, since we don't remove FrameNavigationEntries if
+  // their frames are deleted.  If there is a stale one, remove it to avoid
+  // conflicts on future updates.
+  NavigationEntryImpl* last_committed_entry = static_cast<NavigationEntryImpl*>(
+      parent->navigator()->GetController()->GetLastCommittedEntry());
+  if (last_committed_entry)
+    last_committed_entry->ClearStaleFrameEntriesForNewFrame(added_node);
+
   // Set sandbox flags and make them effective immediately, since initial
   // sandbox flags should apply to the initial empty document in the frame.
   added_node->SetPendingSandboxFlags(sandbox_flags);