Add extra arg isGuest to MatrixClientPeg functions. Add GuestAccess class

GuestAccess serves to monitor which rooms are being tracked for guest
purposes

src/GuestAccess.js

@@ -0,0 +1,52 @@
+/*
+Copyright 2015 OpenMarket Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+import {MatrixClientPeg} from "./MatrixClientPeg";
+const ROOM_ID_KEY = "matrix-guest-room-ids";
+
+class GuestAccess {
+
+    constructor(localStorage) {
+        var existingRoomIds;
+        try {
+            existingRoomIds = JSON.parse(
+                localStorage.getItem(ROOM_ID_KEY) // an array
+            );
+        }
+        catch (e) {} // don't care
+        this.rooms = new Set(existingRoomIds);
+        this.localStorage = localStorage;
+    }
+
+    addRoom(roomId) {
+        this.rooms.add(roomId);
+    }
+
+    removeRoom(roomId) {
+        this.rooms.delete(roomId);
+    }
+
+    getRooms() {
+        return this.rooms.entries();
+    }
+
+    register() {
+        // nuke the rooms being watched from previous guest accesses if any.
+        localStorage.setItem(ROOM_ID_KEY, "[]");
+        return MatrixClientPeg.get().registerGuest();
+    }
+}
+
+module.exports = GuestAccess;