Add local echo for read receipts. Fixes https://github.com/vector-im/vector-web/issues/623

lib/models/room.js

@@ -620,6 +620,17 @@ Room.prototype.addReceipt = function(event) {
     this.emit("Room.receipt", event, this);
 };
 
+/**
+ * Add a temporary local-echo receipt to the room to reflect in the
+ * client the fact that we've sent one.
+ * @param {string} user_id The user ID if the receipt sender
+ * @param {MatrixEvent} e The event that is to be acknowledged
+ * @param {string} receipt_type The type of receipt
+ */
+Room.prototype._addLocalEchoReceipt = function(user_id, e, receipt_type) {
+    this.addReceipt(synthesizeReceipt(user_id, e, receipt_type));
+};
+
 /**
  * Update the room-tag event for the room.  The previous one is overwritten.
  * @param {MatrixEvent} event the m.tag event