Much smaller/managable fix for jashkenas/backbone#3455

We should eventually pull in their changes but for a hope in actually
getting this fix in production I opted to do this instead for now.

bedrock.js

@@ -220,13 +220,29 @@
       for (var id in listeningTo) {
         obj = listeningTo[id];
         obj.off(name, callback, this);
-        if (remove || _.isEmpty(obj._events)) delete this._listeningTo[id];
+        if (remove || !eventsLeftForContext(obj, this)) {
+          delete this._listeningTo[id];
+        }
       }
       return this;
     }
 
   };
 
+  // Fix memory leak reported in https://github.com/jashkenas/backbone/issues/3453
+  // Though their fix is probably better, its a lot larger to try and port right now
+  function eventsLeftForContext(obj, ctx) {
+    var i, l, n;
+    for (n in obj._events) {
+      for (i = 0, l = obj._events[n].length; i < l; i++) {
+        if (obj._events[n][i].ctx === ctx) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
   // Space literal reference used to split event strings.
   var eventSplitter = ' ';
 

test/events.js

@@ -165,21 +165,26 @@
     e.trigger("foo");
   });
 
-  test("stopListening cleans up references", 8, function() {
+  test("stopListening cleans up references", 10, function() {
     var a = _.extend({}, Backbone.Events);
     var b = _.extend({}, Backbone.Events);
     var fn = function() {};
-    a.listenTo(b, 'event', fn).stopListening();
+    b.on('other', fn);
+    a.listenTo(b, 'all', fn).stopListening();
     equal(_.size(a._listeningTo), 0);
-    equal(_.size(b._events), 0);
+    equal(_.size(b._events), 1);
     a.listenTo(b, 'event', fn).stopListening(b);
     equal(_.size(a._listeningTo), 0);
-    equal(_.size(b._events), 0);
+    equal(_.size(b._events), 1);
     a.listenTo(b, 'event', fn).stopListening(b, 'event');
     equal(_.size(a._listeningTo), 0);
-    equal(_.size(b._events), 0);
+    equal(_.size(b._events), 1);
     a.listenTo(b, 'event', fn).stopListening(b, 'event', fn);
     equal(_.size(a._listeningTo), 0);
+    a.listenTo(b, 'event', fn).listenTo(b, 'event', fn).stopListening(null, 'event');
+    equal(_.size(a._listeningTo), 0);
+    equal(_.size(b._events), 1);
+    b.off('other', fn);
     equal(_.size(b._events), 0);
   });