/**
* Remove duplicate VAR declarations.
*/
private void removeDuplicateDeclarations(Node externs, Node root) {
Callback tickler = new ScopeTicklingCallback();
ScopeCreator scopeCreator = new SyntacticScopeCreator(
compiler, new DuplicateDeclarationHandler());
NodeTraversal t = new NodeTraversal(compiler, tickler, scopeCreator);
t.traverseRoots(externs, root);
}