From fa2582a2f13da144dc4eda3e17748beec703d083 Mon Sep 17 00:00:00 2001
From: Tom Payne <twpayne@gmail.com>
Date: Thu, 25 Apr 2013 16:51:28 +0200
Subject: [PATCH] Return listener key from ol.Object#on

---
 src/ol/object.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/ol/object.js b/src/ol/object.js
index 318d1a6482..2007346337 100644
--- a/src/ol/object.js
+++ b/src/ol/object.js
@@ -228,9 +228,10 @@ ol.Object.prototype.notifyInternal_ = function(key) {
  * @param {Function} listener The listener function.
  * @param {Object=} opt_scope Object is whose scope to call
  *     the listener.
+ * @return {?number} Unique key for the listener.
  */
 ol.Object.prototype.on = function(type, listener, opt_scope) {
-  goog.events.listen(this, type, listener, false, opt_scope);
+  return goog.events.listen(this, type, listener, false, opt_scope);
 };