replace another couple of deferreds

src/client.js

@@ -1872,33 +1872,33 @@ MatrixClient.prototype.joinRoom = function(roomIdOrAlias, opts, callback) {
 
     const reqOpts = {qsStringifyOptions: {arrayFormat: 'repeat'}};
 
-    const defer = Promise.defer();
-
     const self = this;
-    sign_promise.then(function(signed_invite_object) {
-        const data = {};
-        if (signed_invite_object) {
-            data.third_party_signed = signed_invite_object;
-        }
+    const prom = new Promise((resolve, reject) => {
+        sign_promise.then(function(signed_invite_object) {
+            const data = {};
+            if (signed_invite_object) {
+                data.third_party_signed = signed_invite_object;
+            }
 
-        const path = utils.encodeUri("/join/$roomid", { $roomid: roomIdOrAlias});
-        return self._http.authedRequest(
-            undefined, "POST", path, queryString, data, reqOpts);
-    }).then(function(res) {
-        const roomId = res.room_id;
-        const syncApi = new SyncApi(self, self._clientOpts);
-        const room = syncApi.createRoom(roomId);
-        if (opts.syncRoom) {
-            // v2 will do this for us
-            // return syncApi.syncRoom(room);
-        }
-        return Promise.resolve(room);
-    }).done(function(room) {
-        _resolve(callback, defer, room);
-    }, function(err) {
-        _reject(callback, defer, err);
+            const path = utils.encodeUri("/join/$roomid", { $roomid: roomIdOrAlias});
+            return self._http.authedRequest(
+                undefined, "POST", path, queryString, data, reqOpts);
+        }).then(function(res) {
+            const roomId = res.room_id;
+            const syncApi = new SyncApi(self, self._clientOpts);
+            const room = syncApi.createRoom(roomId);
+            if (opts.syncRoom) {
+                // v2 will do this for us
+                // return syncApi.syncRoom(room);
+            }
+            return Promise.resolve(room);
+        }).done(function(room) {
+            _resolve(callback, resolve, room);
+        }, function(err) {
+            _reject(callback, reject, err);
+        });
     });
-    return defer.promise;
+    return prom;
 };
 
 /**
@@ -3214,42 +3214,45 @@ MatrixClient.prototype.scrollback = function(room, limit, callback) {
     // reduce the required number of events appropriately
     limit = limit - numAdded;
 
-    const defer = Promise.defer();
+    const self = this;
+    const prom = new Promise((resolve, reject) => {
+        // wait for a time before doing this request
+        // (which may be 0 in order not to special case the code paths)
+        sleep(timeToWaitMs).then(function() {
+            return self._createMessagesRequest(
+                room.roomId,
+                room.oldState.paginationToken,
+                limit,
+                'b');
+        }).done(function(res) {
+            const matrixEvents = utils.map(res.chunk, _PojoToMatrixEventMapper(self));
+            if (res.state) {
+                const stateEvents = utils.map(res.state, _PojoToMatrixEventMapper(self));
+                room.currentState.setUnknownStateEvents(stateEvents);
+            }
+            room.addEventsToTimeline(matrixEvents, true, room.getLiveTimeline());
+            room.oldState.paginationToken = res.end;
+            if (res.chunk.length === 0) {
+                room.oldState.paginationToken = null;
+            }
+            self.store.storeEvents(room, matrixEvents, res.end, true);
+            self._ongoingScrollbacks[room.roomId] = null;
+            _resolve(callback, resolve, room);
+        }, function(err) {
+            self._ongoingScrollbacks[room.roomId] = {
+                errorTs: Date.now(),
+            };
+            _reject(callback, reject, err);
+        });
+    });
+
     info = {
-        promise: defer.promise,
+        promise: prom,
         errorTs: null,
     };
-    const self = this;
-    // wait for a time before doing this request
-    // (which may be 0 in order not to special case the code paths)
-    sleep(timeToWaitMs).then(function() {
-        return self._createMessagesRequest(
-            room.roomId,
-            room.oldState.paginationToken,
-            limit,
-            'b');
-    }).done(function(res) {
-        const matrixEvents = utils.map(res.chunk, _PojoToMatrixEventMapper(self));
-        if (res.state) {
-            const stateEvents = utils.map(res.state, _PojoToMatrixEventMapper(self));
-            room.currentState.setUnknownStateEvents(stateEvents);
-        }
-        room.addEventsToTimeline(matrixEvents, true, room.getLiveTimeline());
-        room.oldState.paginationToken = res.end;
-        if (res.chunk.length === 0) {
-            room.oldState.paginationToken = null;
-        }
-        self.store.storeEvents(room, matrixEvents, res.end, true);
-        self._ongoingScrollbacks[room.roomId] = null;
-        _resolve(callback, defer, room);
-    }, function(err) {
-        self._ongoingScrollbacks[room.roomId] = {
-            errorTs: Date.now(),
-        };
-        _reject(callback, defer, err);
-    });
+
     this._ongoingScrollbacks[room.roomId] = info;
-    return defer.promise;
+    return prom;
 };
 
 /**
@@ -4862,18 +4865,18 @@ function checkTurnServers(client) {
     });
 }
 
-function _reject(callback, defer, err) {
+function _reject(callback, reject, err) {
     if (callback) {
         callback(err);
     }
-    defer.reject(err);
+    reject(err);
 }
 
-function _resolve(callback, defer, res) {
+function _resolve(callback, resolve, res) {
     if (callback) {
         callback(null, res);
     }
-    defer.resolve(res);
+    resolve(res);
 }
 
 function _PojoToMatrixEventMapper(client) {