Create 'type' annotation for 'const' variables

From https://developers.google.com/closure/compiler/docs/js-for-compiler:
  "The type declaration and additional comment are optional. If you
  provide a type declaration, put the declaration on a separate line."

src/ol/source/stamensource.js

@@ -113,7 +113,8 @@ goog.inherits(ol.source.Stamen, ol.source.XYZ);
 
 
 /**
- * @const {Array.<ol.Attribution>}
+ * @const
+ * @type {Array.<ol.Attribution>}
  */
 ol.source.Stamen.ATTRIBUTIONS = [
   new ol.Attribution({