Simplyfy code to gather storage used with StorageManager.estimate()

Documentation:
https://developer.mozilla.org/docs/Web/API/StorageManager

src/js/assets.js

@@ -537,17 +537,7 @@ const assetCacheWrite = function(assetKey, details, callback) {
         if ( details instanceof Object && typeof details.url === 'string' ) {
             entry.remoteURL = details.url;
         }
-        µBlock.cacheStorage.set(
-            { [internalKey]: content }
-        ).then(details => {
-            if (
-                details instanceof Object &&
-                typeof details.bytesInUse === 'number'
-            ) {
-                entry.byteLength = details.bytesInUse;
-            }
-            saveAssetCacheRegistry(true);
-        });
+        µBlock.cacheStorage.set({ assetCacheRegistry, [internalKey]: content });
         const result = { assetKey, content };
         if ( typeof callback === 'function' ) {
             callback(result);
@@ -893,19 +883,6 @@ api.metadata = function(callback) {
 
 /******************************************************************************/
 
-api.getBytesInUse = function() {
-    return getAssetCacheRegistry().then(cacheDict => {
-        let bytesUsed = 0;
-        for ( const assetKey in cacheDict ) {
-            if ( cacheDict.hasOwnProperty(assetKey) === false ) { continue; }
-            bytesUsed += cacheDict[assetKey].byteLength || 0;
-        }
-        return bytesUsed;
-    });
-};
-
-/******************************************************************************/
-
 api.purge = assetCacheMarkAsDirty;
 
 api.remove = function(pattern, callback) {

src/js/cachestorage.js

@@ -215,7 +215,6 @@
                             STORAGE_NAME,
                             { keyPath: 'key' }
                         );
-                        table.createIndex('value', 'value', { unique: false });
                     } catch(ex) {
                         req.onerror();
                     }
@@ -349,22 +348,13 @@
             const entries = [];
             const dontCompress =
                 µBlock.hiddenSettings.cacheStorageCompression !== true;
-            let bytesInUse = 0;
             const handleEncodingResult = result => {
-                if ( typeof result.data === 'string' ) {
-                    bytesInUse += result.data.length;
-                } else if ( result.data instanceof Blob ) {
-                    bytesInUse += result.data.size;
-                }
                 entries.push({ key: result.key, value: result.data });
             };
             for ( const key of keys ) {
                 const data = keyvalStore[key];
                 const isString = typeof data === 'string';
                 if ( isString === false || dontCompress ) {
-                    if ( isString ) {
-                        bytesInUse += data.length;
-                    }
                     entries.push({ key, value: data });
                     continue;
                 }
@@ -379,7 +369,7 @@
                     if ( callback === undefined ) { return; }
                     let cb = callback;
                     callback = undefined;
-                    cb({ bytesInUse });
+                    cb();
                 };
                 try {
                     const transaction = db.transaction(

src/js/storage.js

@@ -50,10 +50,13 @@
         countdown += 1;
         vAPI.storage.getBytesInUse(null, process);
     }
-    if ( this.cacheStorage.name !== 'browser.storage.local' ) {
+    if (
+        navigator.storage instanceof Object &&
+        navigator.storage.estimate instanceof Function
+    ) {
         countdown += 1;
-        this.assets.getBytesInUse().then(count => {
-            process(count);
+        navigator.storage.estimate().then(estimate => {
+            process(estimate.usage);
         });
     }
     if ( countdown === 0 ) {