Fix spurious warning when force-reloading the dashboard

Related issue:
- https://github.com/uBlockOrigin/uBlock-issues/issues/905

Additionally, minor changes to avoid spurious errors in
browser console.

platform/chromium/vapi-common.js

@@ -230,10 +230,22 @@ vAPI.closePopup = function() {
 
 vAPI.localStorage = {
     start: function() {
+        if ( this.cache instanceof Promise ) { return this.cache; }
         if ( this.cache instanceof Object ) { return Promise.resolve(); }
-        if ( this.promise !== undefined ) { return this.promise; }
+        const onChanged = (changes, area) => {
-        this.promise = new Promise(resolve => {
+            if (
+                area !== 'local' ||
+                changes instanceof Object === false ||
+                changes.localStorage instanceof Object === false
+            ) {
+                return;
+            }
+            const newValue = changes.localStorage.newValue;
+            this.cache = newValue instanceof Object ? newValue : {};
+        };
+        this.cache = new Promise(resolve => {
             browser.storage.local.get('localStorage', bin => {
+                this.cache = undefined;
                 if (
                     bin instanceof Object === false ||
                     bin.localStorage instanceof Object === false
@@ -255,22 +267,15 @@ vAPI.localStorage = {
                 if ( this.cache instanceof Object === false ) {
                     this.cache = {};
                 }
-                this.promise = undefined;
-                browser.storage.onChanged.addListener((changes, area) => {
-                    if (
-                        area !== 'local' ||
-                        changes instanceof Object === false ||
-                        changes.localStorage instanceof Object === false
-                    ) {
-                        return;
-                    }
-                    const newValue = changes.localStorage.newValue;
-                    this.cache = newValue instanceof Object ? newValue : {};
-                });
                 resolve();
+                browser.storage.onChanged.addListener(onChanged);
+                self.addEventListener('beforeunload', ( ) => {
+                    this.cache = undefined;
+                    browser.storage.onChanged.removeListener(onChanged);
                 });
             });
-        return this.promise;
+        });
+        return this.cache;
     },
     clear: function() {
         this.cache = {};
@@ -295,11 +300,11 @@ vAPI.localStorage = {
     },
     setItem: function(key, value = undefined) {
         return this.start().then(( ) => {
+            if ( value === this.cache[key] ) { return; }
             this.cache[key] = value;
             return browser.storage.local.set({ localStorage: this.cache });
         });
     },
-    promise: undefined,
     cache: undefined,
 };
 

src/js/dashboard.js

@@ -25,7 +25,8 @@
 
 /******************************************************************************/
 
-(( ) => {
+{
+// >>>>> start of local scope
 
 /******************************************************************************/
 
@@ -82,13 +83,7 @@ const discardUnsavedData = function(synchronous = false) {
     });
 };
 
-const loadDashboardPanel = function(pane = '') {
+const loadDashboardPanel = function(pane, first) {
-    if ( pane === '' ) {
-        vAPI.localStorage.getItemAsync('dashboardLastVisitedPane').then(value => {
-            loadDashboardPanel(value !== null ? value : 'settings.html');
-        });
-        return;
-    }
     const tabButton = uDom(`[href="#${pane}"]`);
     if ( !tabButton || tabButton.hasClass('selected') ) { return; }
     const loadPane = ( ) => {
@@ -98,6 +93,9 @@ const loadDashboardPanel = function(pane = '') {
         uDom.nodeFromId('iframe').setAttribute('src', pane);
         vAPI.localStorage.setItem('dashboardLastVisitedPane', pane);
     };
+    if ( first ) {
+        return loadPane();
+    }
     const r = discardUnsavedData();
     if ( r === false ) { return; }
     if ( r === true ) {
@@ -122,18 +120,22 @@ vAPI.messaging.send('dashboard', {
 });
 
 resizeFrame();
-loadDashboardPanel();
 
-window.addEventListener('resize', resizeFrame);
+vAPI.localStorage.getItemAsync('dashboardLastVisitedPane').then(value => {
-uDom('.tabButton').on('click', onTabClickHandler);
+    loadDashboardPanel(value !== null ? value : 'settings.html', true);
 
-// https://developer.mozilla.org/en-US/docs/Web/API/Window/beforeunload_event
+    window.addEventListener('resize', resizeFrame);
-window.addEventListener('beforeunload', ( ) => {
+    uDom('.tabButton').on('click', onTabClickHandler);
+
+    // https://developer.mozilla.org/en-US/docs/Web/API/Window/beforeunload_event
+    window.addEventListener('beforeunload', ( ) => {
         if ( discardUnsavedData(true) ) { return; }
         event.preventDefault();
         event.returnValue = '';
+    });
 });
 
 /******************************************************************************/
 
-})();
+// <<<<< end of local scope
+}