As far as I can tell, dispatchDidAddBackForwardItem, dispatchDidRemoveBackForwardItem and dispatchDidChangeBackForwardIndex all have no-op implementations in the various FrameLoaderClient implementations. It looks like they were added by http://trac.webkit.org/changeset/51629 for the old Android port. I assume they're no longer needed for the new (Chromium-based) one?
It's unlikely they'll be needed by the new Android port because it shares its back/forward logic with the other Chromium ports.
I'll remove them.
Created attachment 107753 [details]
Will wait for the EWS to go through this patch before trying to land it.
Comment on attachment 107753 [details]
Clearing flags on attachment: 107753
Committed r95387: <http://trac.webkit.org/changeset/95387>
All reviewed patches have been landed. Closing bug.