[Files app] ES6 class for multi_metadata_provider.js

Bug: 778674
Change-Id: Ib270ab8c6f7ddc916d724ae8e0d64bbce22031ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1647643
Commit-Queue: François Degros <fdegros@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Auto-Submit: François Degros <fdegros@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666618}

ui/file_manager/file_manager/foreground/js/metadata/multi_metadata_provider.js

@@ -2,77 +2,40 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-/**
+/** @final */
+class MultiMetadataProvider extends MetadataProvider {
+  /**
    * @param {!FileSystemMetadataProvider} fileSystemMetadataProvider
    * @param {!ExternalMetadataProvider} externalMetadataProvider
    * @param {!ContentMetadataProvider} contentMetadataProvider
    * @param {!VolumeManager} volumeManager
- * @constructor
- * @extends {MetadataProvider}
- * @struct
    */
-function MultiMetadataProvider(
+  constructor(
       fileSystemMetadataProvider, externalMetadataProvider,
       contentMetadataProvider, volumeManager) {
-  MetadataProvider.call(
-      this,
-      FileSystemMetadataProvider.PROPERTY_NAMES
+    super(FileSystemMetadataProvider.PROPERTY_NAMES
               .concat(ExternalMetadataProvider.PROPERTY_NAMES)
               .concat(ContentMetadataProvider.PROPERTY_NAMES));
 
-  /**
-   * @private {!FileSystemMetadataProvider}
-   * @const
-   */
+    /** @private @const {!FileSystemMetadataProvider} */
     this.fileSystemMetadataProvider_ = fileSystemMetadataProvider;
 
-  /**
-   * @private {!ExternalMetadataProvider}
-   * @const
-   */
+    /** @private @const {!ExternalMetadataProvider} */
     this.externalMetadataProvider_ = externalMetadataProvider;
 
-  /**
-   * @private {!ContentMetadataProvider}
-   * @const
-   */
+    /** @private @const {!ContentMetadataProvider} */
     this.contentMetadataProvider_ = contentMetadataProvider;
 
-  /**
-   * @private {!VolumeManager}
-   * @const
-   */
+    /** @private @const {!VolumeManager} */
     this.volumeManager_ = volumeManager;
-}
-
-MultiMetadataProvider.prototype.__proto__ = MetadataProvider.prototype;
-
-/**
- * Property names of documents-provider files which we should get from
- * ExternalMetadataProvider.
- *
- * We should NOT use ExternalMetadataProvider.PROPERTY_NAMES for
- * documents-provider files, since ExternalMetadataProvider zero-fills all
- * requested properties (e.g. 'size' is initialized to '0 bytes' even when size
- * is not acquired by chrome.fileManagerPrivate.getEntryProperties) and the
- * zero-filled property can overwrite a valid property which is already
- * acquired from FileSystemMetadataProvider.
- *
- * @const {!Array<string>}
- */
-MultiMetadataProvider.DOCUMENTS_PROVIDER_EXTERNAL_PROPERTY_NAMES = [
-  'canCopy',
-  'canDelete',
-  'canRename',
-  'canAddChildren',
-];
+  }
 
-/**
+  /**
    * Obtains metadata for entries.
    * @param {!Array<!MetadataRequest>} requests
    * @return {!Promise<!Array<!MetadataItem>>}
    */
-MultiMetadataProvider.prototype.get = function(requests) {
+  get(requests) {
     const fileSystemRequests = [];
     const externalRequests = [];
     const contentRequests = [];
@@ -161,7 +124,8 @@ MultiMetadataProvider.prototype.get = function(requests) {
     };
     const fileSystemPromise =
         get(this.fileSystemMetadataProvider_, fileSystemRequests);
-  const externalPromise = get(this.externalMetadataProvider_, externalRequests);
+    const externalPromise =
+        get(this.externalMetadataProvider_, externalRequests);
     const contentPromise = get(this.contentMetadataProvider_, contentRequests);
     const fallbackContentPromise = externalPromise.then(requestsAndResults => {
       const requests = requestsAndResults.requests;
@@ -201,7 +165,29 @@ MultiMetadataProvider.prototype.get = function(requests) {
             }
           }
           return requests.map(request => {
-          return integratedResults[request.entry.toURL()] || new MetadataItem();
+            return integratedResults[request.entry.toURL()] ||
+                new MetadataItem();
           });
         });
-};
+  }
+}
+
+/**
+ * Property names of documents-provider files which we should get from
+ * ExternalMetadataProvider.
+ *
+ * We should NOT use ExternalMetadataProvider.PROPERTY_NAMES for
+ * documents-provider files, since ExternalMetadataProvider zero-fills all
+ * requested properties (e.g. 'size' is initialized to '0 bytes' even when size
+ * is not acquired by chrome.fileManagerPrivate.getEntryProperties) and the
+ * zero-filled property can overwrite a valid property which is already
+ * acquired from FileSystemMetadataProvider.
+ *
+ * @const {!Array<string>}
+ */
+MultiMetadataProvider.DOCUMENTS_PROVIDER_EXTERNAL_PROPERTY_NAMES = [
+  'canCopy',
+  'canDelete',
+  'canRename',
+  'canAddChildren',
+];