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 35603af62ed8e4891ecf8176d6e9ccb43e5f7f99..75c53076240fdf32003247eedfb53300b604e5b4 100644
--- a/content/browser/frame_host/navigation_entry_impl.h
+++ b/content/browser/frame_host/navigation_entry_impl.h
@@ -233,6 +233,10 @@ class CONTENT_EXPORT NavigationEntryImpl
   // during session history navigations, when the child items no longer apply.
   void ClearChildren(FrameTreeNode* frame_tree_node);
 
+  // Removes subframe FrameNavigationEntry matching the |frame_unique_name| and

[Charlie Reis, 2016/07/27 22:48:28]

nit: Removes the
nit: ... |frame_unique_name|, if any, and...

Maybe we should also document that this will remove all such FNEs, but that we
expect there to be at most 1 (and will DCHECK otherwise).

[nasko, 2016/07/29 15:52:22]

What does documenting this here give us? It will be adding description of what
bugs we might have, which the DCHECK is aimed at catching in the first place.

[Charlie Reis, 2016/07/29 17:21:35]

I think it matters for potential callers of the method.  For example, this
method would not guarantee the current bug is fixed if it were implemented as
described (i.e., it stopped after the first one), because there could still be
more colliding FNEs in the tree.

We don't need to mention the DCHECK, but I think we can still clarify:

Removes any subframe FrameNavigationEntries that match the unique name of
|frame_tree_node|, and all of their children.  We expect there to be at most
one, since we avoid collisions but leave old FrameNavigationEntries in the tree
after their frame has been detached.

[nasko, 2016/08/01 20:42:15]

Done.

+  // all of its children.
+  void ClearNamedFrameEntries(const std::string& frame_unique_name);
+
   void set_unique_id(int unique_id) {
     unique_id_ = unique_id;
   }