delete sync data when LL is toggled, show message when enabling

src/Lifecycle.js

@@ -31,6 +31,7 @@ import RtsClient from './RtsClient';
 import Modal from './Modal';
 import sdk from './index';
 import ActiveWidgetStore from './stores/ActiveWidgetStore';
+import PlatformPeg from "./PlatformPeg";
 
 /**
  * Called at startup, to attempt to build a logged-in Matrix session. It tries
@@ -237,6 +238,27 @@ async function _restoreFromLocalStorage() {
 function _handleLoadSessionFailure(e) {
     console.log("Unable to load session", e);
 
+    if (e instanceof Matrix.InvalidStoreError) {
+        if (e.reason === Matrix.InvalidStoreError.TOGGLED_LAZY_LOADING) {
+            const LazyLoadingResyncDialog =
+                sdk.getComponent("views.dialogs.LazyLoadingResyncDialog");
+            return Promise.resolve().then(() => {
+                const lazyLoadEnabled = e.value;
+                if (lazyLoadEnabled) {
+                    return new Promise((resolve) => {
+                        Modal.createDialog(LazyLoadingResyncDialog, {
+                            onFinished: resolve,
+                        });
+                    });
+                }
+            }).then(() => {
+                return MatrixClientPeg.get().store.deleteAllData();
+            }).then(() => {
+                PlatformPeg.get().reload();
+            });
+        }
+    }
+
     const def = Promise.defer();
     const SessionRestoreErrorDialog =
           sdk.getComponent('views.dialogs.SessionRestoreErrorDialog');

src/components/views/dialogs/LazyLoadingResyncDialog.js

@@ -0,0 +1,32 @@
+/*
+Copyright 2015, 2016 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 React from 'react';
+import QuestionDialog from './QuestionDialog';
+import { _t } from '../../../languageHandler';
+
+export default (props) => {
+    const description =
+        _t("Lazy loading has been enabled for your account. Performance!! We'll need to resync your account.");
+
+    return (<QuestionDialog
+        hasCancelButton={false}
+        title={_t("Need to resync your account")}
+        description={<div>{description}</div>}
+        button={_t("OK")}
+        onFinished={props.onFinished}
+    />);
+};