TimerView: don't continue to update after expiration

FREEBIE

js/models/messages.js

@@ -508,6 +508,9 @@
         isExpiring: function() {
             return this.get('expireTimer') && this.get('expirationStartTimestamp');
         },
+        isExpired: function() {
+            return this.msTilExpire() <= 0;
+        },
         msTilExpire: function() {
               if (!this.isExpiring()) {
                 return Infinity;

js/views/message_view.js

@@ -36,6 +36,9 @@
               clearTimeout(this.timeout);
               this.timeout = null;
             }
+            if (this.model.isExpired()) {
+                return this;
+            }
             if (this.model.isExpiring()) {
                 this.render();
                 var totalTime = this.model.get('expireTimer') * 1000;