Introduce base/storage to represent the Web Storage API and persistence-related customizations

react/features/app/components/AbstractApp.js

 } from '../../base/participants';
 import { getProfile } from '../../base/profile';
 import { Fragment, RouteRegistry } from '../../base/react';
-import {
-    MiddlewareRegistry,
-    PersistencyRegistry,
-    ReducerRegistry
-} from '../../base/redux';
+import { MiddlewareRegistry, ReducerRegistry } from '../../base/redux';
+import { PersistenceRegistry } from '../../base/storage';
 import { toURLString } from '../../base/util';
 import { OverlayContainer } from '../../overlay';
 import { BlankPage } from '../../welcome';
         return (
             createStore(
                 reducer,
-                PersistencyRegistry.getPersistedState(),
+                PersistenceRegistry.getPersistedState(),
                 middleware));
     }
 

react/features/base/lib-jitsi-meet/native/polyfills-browser.js

 
 import { Platform } from '../../react';
 
-import Storage from './Storage';
+// XXX The library lib-jitsi-meet utilizes window.localStorage at the time of
+// this writing and, consequently, the browser-related polyfills implemented
+// here by the feature base/lib-jitsi-meet for the purposes of the library
+// lib-jitsi-meet are incomplete without the Web Storage API! Should the library
+// lib-jitsi-meet (and its dependencies) stop utilizing window.localStorage,
+// the following import may be removed:
+import '../../storage';
 
 /**
  * Gets the first common prototype of two specified Objects (treating the
         global.document = document;
     }
 
-    // localStorage
-    if (typeof global.localStorage === 'undefined') {
-        global.localStorage = new Storage('@jitsi-meet/');
-    }
-
     // location
     if (typeof global.location === 'undefined') {
         global.location = {
         navigator.userAgent = userAgent;
     }
 
-    // sessionStorage
-    //
-    // Required by:
-    // - herment
-    // - Strophe
-    if (typeof global.sessionStorage === 'undefined') {
-        global.sessionStorage = new Storage();
-    }
-
     // WebRTC
     require('./polyfills-webrtc');
     require('react-native-callstats/csio-polyfill');

react/features/base/profile/reducer.js

 // @flow
 
-import { PersistencyRegistry, ReducerRegistry } from '../redux';
+import { ReducerRegistry } from '../redux';
+import { PersistenceRegistry } from '../storage';
 
 import { PROFILE_UPDATED } from './actionTypes';
 
 
 const STORE_NAME = 'features/base/profile';
 
-PersistencyRegistry.register(STORE_NAME, {
+/**
+ * Sets up the persistence of the feature base/profile.
+ */
+PersistenceRegistry.register(STORE_NAME, {
     profile: true
 });
 

react/features/base/redux/index.js

 export * from './functions';
 export { default as MiddlewareRegistry } from './MiddlewareRegistry';
-export { default as PersistencyRegistry } from './PersistencyRegistry';
 export { default as ReducerRegistry } from './ReducerRegistry';
-
-import './middleware';

react/features/base/redux/readme.md

-Jitsi Meet - redux state persistency
-====================================
-Jitsi Meet has a persistency layer that persists a subtree (or specific subtrees) into window.localStorage (on web) or
-AsyncStorage (on mobile).
-
-Usage
-=====
-If a subtree of the redux store should be persisted (e.g. ``'features/base/profile'``), then persistency for that
-subtree should be requested by registering the subtree (and related config) into PersistencyRegistry.
-
-E.g. to register the field ``profile`` of the Redux subtree ``'features/base/profile'`` to be persisted, use:
-
-```JavaScript
-PersistencyRegistry.register('features/base/profile', {
-    profile: true
-});
-```
-
-in the ``reducer.js`` of the ``profile`` feature.
-
-When it's done, Jitsi Meet will automatically persist these subtrees/fields and rehidrate them on startup.
-
-Throttling
-==========
-To avoid too frequent write operations in the storage, we utilise throttling in the persistency layer, meaning that the storage
-gets persisted only once in every 2 seconds, even if multiple redux state changes occur during this period. This throttling timeout
-can be configured in
-```
-react/features/base/redux/middleware.js#PERSIST_DELAY
-```

react/features/base/redux/PersistencyRegistry.js → react/features/base/storage/PersistenceRegistry.js

  * A registry to allow features to register their redux store subtree to be
  * persisted and also handles the persistency calls too.
  */
-class PersistencyRegistry {
+class PersistenceRegistry {
     _checksum: string;
 
     _elements: PersistencyConfigMap;
 
     /**
-     * Initializes a new {@ code PersistencyRegistry} instance.
+     * Initializes a new {@ code PersistenceRegistry} instance.
      */
     constructor() {
         this._elements = {};
     }
 }
 
-export default new PersistencyRegistry();
+export default new PersistenceRegistry();

react/features/base/storage/README.md

+Jitsi Meet - redux state persistence
+====================================
+Jitsi Meet has a persistence layer that persists specific subtrees of the redux
+store/state into window.localStorage (on Web) or AsyncStorage (on mobile).
+
+Usage
+=====
+If a subtree of the redux store should be persisted (e.g.
+`'features/base/profile'`), then persistence for that subtree should be
+requested by registering the subtree with `PersistenceRegistry`.
+
+For example, to register the field `profile` of the redux subtree
+`'features/base/profile'` to be persisted, use:
+```javascript
+PersistenceRegistry.register('features/base/profile', {
+    profile: true
+});
+```
+
+in the `reducer.js` of the `base/profile` feature.
+
+When it's done, Jitsi Meet will automatically persist these subtrees and
+rehydrate them on startup.
+
+Throttling
+==========
+To avoid too frequent write operations in the storage, we utilize throttling in
+the persistence layer, meaning that the storage gets persisted only once every 2
+seconds, even if multiple redux state changes occur during this period. The
+throttling timeout can be configured in
+```
+react/features/base/storage/middleware.js#PERSIST_STATE_DELAY
+```

react/features/base/storage/_.native.js

+export * from './native';

react/features/base/storage/index.js

+export * from './_';
+export { default as PersistenceRegistry } from './PersistenceRegistry';
+
+import './middleware';

react/features/base/redux/middleware.js → react/features/base/storage/middleware.js

 
 import _ from 'lodash';
 
-import { toState } from './functions';
-import MiddlewareRegistry from './MiddlewareRegistry';
-import PersistencyRegistry from './PersistencyRegistry';
+import { MiddlewareRegistry, toState } from '../redux';
+
+import PersistenceRegistry from './PersistenceRegistry';
 
 /**
- * The delay that passes between the last state change and the persisting of
- * that state in the storage.
+ * The delay in milliseconds that passes between the last state change and the
+ * persisting of that state in the storage.
  */
 const PERSIST_STATE_DELAY = 2000;
 
  */
 const throttledPersistState
     = _.throttle(
-        state => PersistencyRegistry.persistState(state),
+        state => PersistenceRegistry.persistState(state),
         PERSIST_STATE_DELAY);
 
 /**
  * A master MiddleWare to selectively persist state. Please use the
- * {@link persisterconfig.json} to set which subtrees of the Redux state should
+ * {@link persisterconfig.json} to set which subtrees of the redux state should
  * be persisted.
  *
  * @param {Store} store - The redux store.
  * @returns {Function}
  */
 MiddlewareRegistry.register(store => next => action => {
+    const oldState = toState(store);
     const result = next(action);
+    const newState = toState(store);
 
-    throttledPersistState(toState(store));
+    oldState === newState || throttledPersistState(newState);
 
     return result;
 });

react/features/base/storage/native/index.js

+import './polyfills-browser';

react/features/base/storage/native/polyfills-browser.js

+import Storage from './Storage';
+
+(global => {
+
+    // localStorage
+    if (typeof global.localStorage === 'undefined') {
+        global.localStorage = new Storage('@jitsi-meet/');
+    }
+
+    // sessionStorage
+    //
+    // Required by:
+    // - herment
+    // - Strophe
+    if (typeof global.sessionStorage === 'undefined') {
+        global.sessionStorage = new Storage();
+    }
+
+})(global || window || this); // eslint-disable-line no-invalid-this

react/features/recent-list/components/AbstractRecentList.js

 }
 
 /**
- * Maps Redux state to component props.
+ * Maps redux state to component props.
  *
  * @param {Object} state - The redux state.
  * @returns {{

react/features/recent-list/reducer.js

 // @flow
 
-import { PersistencyRegistry, ReducerRegistry } from '../base/redux';
+import { ReducerRegistry } from '../base/redux';
+import { PersistenceRegistry } from '../base/storage';
 
 import {
     STORE_CURRENT_CONFERENCE,
 const STORE_NAME = 'features/recent-list';
 
 /**
- * Registers the redux store subtree of this feature for persistency.
+ * Sets up the persistence of the feature recent-list.
  */
-PersistencyRegistry.register(STORE_NAME, {
+PersistenceRegistry.register(STORE_NAME, {
     list: true
 });
 
 /**
- * Reduces the redux actions of the feature features/recent-list.
+ * Reduces the redux actions of the feature recent-list.
  */
 ReducerRegistry.register(
     STORE_NAME,