Add MatrixClient.setGuestRooms

This is used in /events to grab events for the rooms the Guest is interested
in.

lib/client.js

@@ -153,6 +153,8 @@ function MatrixClient(opts) {
     }
     this._syncState = null;
     this._syncingRetry = null;
+
+    this._guestRooms = null;
 }
 utils.inherits(MatrixClient, EventEmitter);
 
@@ -1789,6 +1791,14 @@ MatrixClient.prototype.registerGuest = function(opts, callback) {
     );
 };
 
+/**
+ * Set a list of rooms the Guest is interested in receiving events from.
+ * @param {String[]} A list of room IDs.
+ */
+MatrixClient.prototype.setGuestRooms = function(roomIds) {
+    this._guestRooms = roomIds;
+};
+
 /**
  * @param {string} username
  * @param {string} password
@@ -2220,10 +2230,16 @@ function _pollForEvents(client, attempt) {
         _pollForEvents(client);
     }, timeoutMs + (20 * 1000)); // 20s buffer
 
-    client._http.authedRequest(undefined, "GET", "/events", {
+    var queryParams = {
         from: client.store.getSyncToken(),
         timeout: timeoutMs
-    }).done(function(data) {
+    };
+    if (client._guestRooms) {
+        queryParams.room_id = client._guestRooms;
+    }
+
+    client._http.authedRequest(undefined, "GET", "/events", queryParams).done(
+    function(data) {
         if (discardResult) {
             return;
         }