Polymer and GWT integration with JS Interop

PolymerGwt.java

public class PolymerEntryPoint implements EntryPoint {

	@Override
	public void onModuleLoad() {
		PaperButton paperButton = Browser.createPaperButton();
		FlowPanel panel = new FlowPanel();
		RootPanel.get().add(panel);
		
		UiBinderExample paperbuttonUiExample = new UiBinderExample();
		
		panel.add(paperbuttonUiExample);
		
		Browser.append(panel.getElement(), paperButton);
	}
}

public class UiBinderExample extends Composite {

	private static UiBinderExampleBinder uiBinder = GWT.create(UiBinderExampleBinder.class);

	interface UiBinderExampleBinder extends UiBinder<Widget, UiBinderExample> {
	}

	public UiBinderExample() {
		initWidget(uiBinder.createAndBindUi(this));
		paperButton.setInnerText("through binder");
	}

	@UiField PaperButton paperButton;
}

/**
<!DOCTYPE ui:UiBinder SYSTEM "http://dl.google.com/gwt/DTD/xhtml.ent">
<ui:UiBinder xmlns:ui="urn:ui:com.google.gwt.uibinder"
	xmlns:g="urn:import:com.google.gwt.user.client.ui">
	<g:HTMLPanel>
		<paper-button ui:field="paperButton"></paper-button>
	</g:HTMLPanel>
</ui:UiBinder> 
**/

public class Browser {

        public static native Document getDocument() /*-{
	 	return $doc;
	}-*/;
  
	public static native void append(com.google.gwt.dom.client.Element parent, HTMLElement child) /*-{
		parent.appendChild(child);
	}-*/;
	
	public static PaperButton createPaperButton() {
		PaperButton paperButton = (PaperButton) Browser.getDocument().createElement("paper-button");
		paperButton.setInnerText("PAPER BUTTON");
		return paperButton;
	}
}

@JsType
public interface PaperButton extends HTMLElement {
	
}

@JsType(prototype = "HTMLElement")
public interface HTMLElement extends Element {

    public void setAttribute(String id, String value);
    
    public String getAttribute(String id);

    public void appendChild(HTMLElement element);

    @JsProperty
    public void setInnerHTML(String text);

    @JsProperty
    public void setInnerText(String text);
}

@JsType(isNative = true, prototype = "Document")
public interface Document {

    public HTMLElement createElement(String div);

    public HTMLElement getElementById(String id);
}