Eu aplico um costumeView aoActionBar, como isso

// Inflate the "Done/Discard" custom ActionBar view.
LayoutInflater inflater = (LayoutInflater) DetailsHost.mActionBar
        .getThemedContext().getSystemService(DetailsHost.LAYOUT_INFLATER_SERVICE);
final View customActionBarView = inflater.inflate(
        R.layout.actionbar_custom_view_done_discard, null);

// Show the custom ActionBar view and hide the normal Home icon and title.
DetailsHost.mActionBar.setDisplayOptions(
        ActionBar.DISPLAY_SHOW_CUSTOM,
        ActionBar.DISPLAY_SHOW_CUSTOM | ActionBar.DISPLAY_SHOW_HOME
                | ActionBar.DISPLAY_SHOW_TITLE);
DetailsHost.mActionBar.setCustomView(customActionBarView, 
        new ActionBar.LayoutParams(
                ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.MATCH_PARENT));

(baseado no código Roman Nuriks).

Como faço para restaurar o layout inicial? Nota: eu uso o ActionBarSherlock