The document you get from Designer isn’t really a HTML page even though it might look like it. It’s just a textual representation that will be parsed turned into Java bytecode. There are ways to include Polymer elements into your Vaadin app, but it’s a bit more complicated than that. If you’re using Vaadin 7, see
https://github.com/Artur-/date-picker for an example. In Vaadin 8, you should be able to use the @HtmlImport annotation, see
https://vaadin.com/framework/whatsnew and the HTML imports section.
I tryed to use @HtmlImport annotation inside Liferay DXP : @HtmlImport(“vaadin://bower_components/vaadin-combo-box/vaadin-combo-box.html”)
But I received the following exception:
17:50:01,882 WARN [http-nio-7007-exec-10]