private DocRef getSelectedDoc(final TabData selectedTab) {
        if (selectedTab instanceof DocumentTabData) {
            //noinspection PatternVariableCanBeUsed // Not in GWT
            final DocumentTabData documentTabData = (DocumentTabData) selectedTab;
            return documentTabData.getDocRef();
        }
        return null;
    }
Highlights the supplied document item in the explorer tree.
stroom-core-client/src/main/java/stroom/document/client/DocumentPluginEventManager.java