Where is ContentWidget.CwConstants located and what is it?

Question

I´ve just started learning GWT and I´m trying to implement http://gwt.google.com/samples/Showcase/Showcase.html#!CwFileUpload and but failing miserably.

Where is the ContentWidget.CwConstants suppose to come from and what exactly is it?

public static interface CwConstants extends Constants,
      ContentWidget.CwConstants {
    String cwFileUploadButton();

    String cwFileUploadDescription();

    String cwFileUploadName();

String cwFileUploadNoFileError();

String cwFileUploadSelectFile();

    String cwFileUploadSuccessful();
  }

Answer 1

Take a look at the source tree of the samples in the GWT code project. There you also find the class you are looking for: http://code.google.com/p/google-web-toolkit/source/browse/trunk/samples/showcase/src/com/google/gwt/sample/showcase/client/ContentWidget.java