docs: protected String getResponseContentType(FacesContext context, String orig)
      {
          String contentType = orig;
  
          // see if we need to override the contentType
          Map<Object, Object> m = context.getAttributes();
          if (m.containsKey("facelets.ContentType"))
          {
              contentType = (String) m.get("facelets.ContentType");
              if (log.isLoggable(Level.FINEST))
              {
                  log.finest("Facelet specified alternate contentType '" + contentType + "'");
              }
          }
  
          // safety check
          if (contentType == null)
          {
              contentType = "text/html";
              log.finest("ResponseWriter created had a null ContentType, defaulting to text/html");
          }
  
          return contentType;
      }