I think this needs to be refactored since it's not closing all documents in this case.  Just make it a function in DocumentManager.closeDocuments() and just call that function directly from here.

The code in Document.js can be refactored so that FILE_CLOSE_ALL calls that function and just passes it the array of files from the working.  I would also do the work of checking for unsaved documents in this function so that you don't have to do it in 2 places.  closeDocuments() can just figure out which documents have unsaved changes and prompt for those and close the rest.  Then you don't need the code inside this execute promise as well.