ConversationView.markRead: Mark all messages read when at bottom

To handle the same 'not quite at the bottom' case that our 30px buffer
gives us for marking messages read, we use the same atBottom() method to
determine whether we should mark everything unread. Saves the effort and
potential missed messages (due to partial pixels, etc.).

FREEBIE

js/views/conversation_view.js

@@ -217,7 +217,8 @@
         },
         updateUnread: function() {
             this.resetLastSeenIndicator();
-            this.markRead();
+            // Waiting for scrolling caused by resetLastSeenIndicator to settle down
+            setTimeout(this.markRead.bind(this), 1);
         },
 
         onOpened: function() {
@@ -418,7 +419,7 @@
 
         onClick: function(e) {
             this.closeMenu(e);
-            this.markRead(e);
+            this.markRead();
         },
 
         findNewestVisibleUnread: function() {
@@ -468,8 +469,15 @@
             }
         },
 
-        markRead: function(e) {
-            var unread = this.findNewestVisibleUnread();
+        markRead: function() {
+            var unread;
+
+            if (this.view.atBottom()) {
+                unread = this.model.messageCollection.last();
+            } else {
+                unread = this.findNewestVisibleUnread();
+            }
+
             if (unread) {
                 this.model.markRead(unread.get('received_at'));
             }