From your Dojo library project, copy toolkit/dojo/dojo/nls/core-web-layer_ROOT.js
and toolkit/dojo/dojo/nls/mobile-ui-layer_ROOT.js
into your Worklight project's www/dojo/nls
folder.
Additionally, if your phone is not set for the en-US locale, you may need to copy additional resources from the Dojo library project. For example, if your phone is configured for French, you'd need to copy toolkit/dojo/dojo/nls/core-web-layer_fr.js
and toolkit/dojo/dojo/nls/mobile-ui-layer_fr.js
into your Worklight project's www/dojo/nls
folder as well.