Make color parser more resilient against JavaScript errors

A major usability issue is encountered in Designer when it meets basic syntactic issues in the script part, e.g. the following code misses a single comma "," and the file cannot be rendered in the layout view:

  Polymer({
    is: 'nuxeo-file-view-layout',
    behaviors: [Nuxeo.LayoutBehavior],
    properties: {
      /**
         * @doctype File
         */
      document: Object
      bug: Object
    }
  });

You have to delete the file and recreate it to be able to correct, or glance at:
https://connect.nuxeo.com/nuxeo/designer/#/PROJECT/resources/ui/document/file/nuxeo-file-view-layout.html to decipher what's wrong.

A visual RED ALERT for JavaScript syntactic errors would be much appreciated, as is already the case for the XML part of the layout.