Bump to v4.16.0.

_mapCacheSet.js

@@ -11,7 +11,11 @@ import getMapData from './_getMapData.js';
  * @returns {Object} Returns the map cache instance.
  */
 function mapCacheSet(key, value) {
-  getMapData(this, key).set(key, value);
+  var data = getMapData(this, key),
+      size = data.size;
+
+  data.set(key, value);
+  this.size += data.size == size ? 0 : 1;
   return this;
 }