Allow user selection in overlay container

src/ol/css.js

@@ -10,6 +10,14 @@ goog.provide('ol.css');
 ol.css.CLASS_HIDDEN = 'ol-hidden';
 
 
+/**
+ * The CSS class that we'll give the DOM elements to have them selectable.
+ *
+ * @const
+ * @type {string}
+ */
+ol.css.CLASS_SELECTABLE = 'ol-selectable';
+
 /**
  * The CSS class that we'll give the DOM elements to have them unselectable.
  *