lib/Ext/app/History.js
function() {
        var actions = this.getActions(),
            previousAction = actions[actions.length - 2];

        if (previousAction) {
            actions.pop();

            previousAction.getController().getApplication().redirectTo(previousAction.getUrl());
        }
        else {
            actions[actions.length - 1].getController().getApplication().redirectTo('');
        }
    }
function() {
        var actions = this.getActions(),
            previousAction = actions[actions.length - 2];

        if (previousAction) {
            actions.pop();

            previousAction.getController().getApplication().redirectTo(previousAction.getUrl());
        }
        else {
            actions[actions.length - 1].getController().getApplication().redirectTo('');
        }
    }
Navigate to the previous active action. This changes the page url.