ref(app): move initialization into componentDidMount

componentWillMount is a deprecated lifecycle method;
componentDidMount should be used to kick off things
like ajax. In the case of the _App hierarchy, a promise
chain is used to perform initialization, and it is
first started in the constructor by initializing
storage. However, by the time storage is initialized,
resolving the first promise, _App has already mounted.
So, move it all to the componentDidMount lifecycle.

react/features/app/components/AbstractApp.js

      *
      * @inheritdoc
      */
-    componentWillMount() {
-        super.componentWillMount();
+    componentDidMount() {
+        super.componentDidMount();
 
         this._init.then(() => {
             // If a URL was explicitly specified to this React Component, then

react/features/app/components/App.native.js

      * @returns {void}
      * @see https://facebook.github.io/react-native/docs/linking.html
      */
-    componentWillMount() {
-        super.componentWillMount();
+    componentDidMount() {
+        super.componentDidMount();
 
         Linking.addEventListener('url', this._onLinkingURL);
     }

react/features/base/app/components/BaseApp.js

             // $FlowFixMe
             store: undefined
         };
+    }
 
+    /**
+     * Initializes the app.
+     *
+     * @inheritdoc
+     */
+    componentDidMount() {
         /**
          * Make the mobile {@code BaseApp} wait until the {@code AsyncStorage}
          * implementation of {@code Storage} initializes fully.
          * @see {@link #_initStorage}
          * @type {Promise}
          */
-        this._init
-            = this._initStorage()
-                .catch(() => { /* AbstractApp should always initialize! */ })
-                .then(() =>
-                    this.setState({
-                        store: this._createStore()
-                    }));
-    }
-
-    /**
-     * Initializes the app.
-     *
-     * @inheritdoc
-     */
-    componentWillMount() {
-        this._init.then(() => this.state.store.dispatch(appWillMount(this)));
+        this._init = this._initStorage()
+            .catch(() => { /* BaseApp should always initialize! */ })
+            .then(() => new Promise(resolve => {
+                this.setState({
+                    store: this._createStore()
+                }, resolve);
+            }))
+            .then(() => this.state.store.dispatch(appWillMount(this)))
+            .catch(() => { /* BaseApp should always initialize! */ });
     }
 
     /**

react/features/mobile/incoming-call/components/IncomingCallApp.js

      *
      * @returns {void}
      */
-    componentWillMount() {
-        super.componentWillMount();
+    componentDidMount() {
+        super.componentDidMount();
 
         this._init.then(() => {
             const { dispatch } = this.state.store;