Bump to v4.6.0.

_addMapEntry.js

@@ -9,6 +9,7 @@ define([], function() {
    * @returns {Object} Returns `map`.
    */
   function addMapEntry(map, pair) {
+    // Don't return `Map#set` because it doesn't return the map instance in IE 11.
     map.set(pair[0], pair[1]);
     return map;
   }