Fix js compilation error introduced in CL 954943006.

TBR=dbeam
NOTRY=true

Review URL: https://codereview.chromium.org/960313002

Cr-Commit-Position: refs/heads/master@{#318251}

ui/file_manager/file_manager/background/js/media_import_handler.js

@@ -400,7 +400,7 @@ importer.MediaImportHandler.ImportTask.prototype.copy_ =
    */
   var onComplete = function(destinationEntry) {
     this.cancelCallback_ = null;
-    this.markAsCopied_(entry, destinationEntry);
+    this.markAsCopied_(entry, /** @type {!FileEntry} */ (destinationEntry));
     this.notify(importer.TaskQueue.UpdateType.PROGRESS);
     resolver.resolve(destinationEntry);
   };