Update conversation snippets automatically

Fixes stale snippets after the message has expired

js/models/conversations.js

@@ -167,6 +167,18 @@
         }.bind(this));
     },
 
+    updateLastMessage: function() {
+        var lastMessage = this.messageCollection.at(this.messageCollection.length - 1);
+        if (lastMessage) {
+          this.save({
+            lastMessage : lastMessage.getNotificationText(),
+            timestamp   : lastMessage.get('sent_at')
+          });
+        } else {
+          this.save({ lastMessage: '', timestamp: null });
+        }
+    },
+
     addExpirationTimerUpdate: function(time, source) {
         var now = Date.now();
         this.save({ expireTimer: time });

js/views/conversation_list_item_view.js

@@ -20,6 +20,8 @@
             this.listenTo(this.model, 'change', _.debounce(this.render.bind(this), 1000));
             this.listenTo(this.model, 'destroy', this.remove); // auto update
             this.listenTo(this.model, 'opened', this.markSelected); // auto update
+            this.listenTo(this.model.messageCollection, 'add remove',
+              _.debounce(this.model.updateLastMessage.bind(this.model), 1000));
             extension.windows.onClosed(this.stopListening.bind(this));
             this.timeStampView = new Whisper.TimestampView({brief: true});
         },