Give an app the file entries it had back on restart.

chrome/renderer/resources/extensions/file_system_custom_bindings.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Custom binding for the fileSystem API.
 
 var binding = require('binding').Binding.create('fileSystem');
 
 var entryIdManager = require('entryIdManager');
 var fileSystemNatives = requireNative('file_system_natives');
@@ skipping 18 matching lines @@
 
   function bindFileEntryCallback(i, functionName) {
     apiFunctions.setCustomCallback(functionName,
         function(name, request, response) {
       if (request.callback && response) {
         var callback = request.callback;
         request.callback = null;
 
         var fileSystemId = response.fileSystemId;
         var baseName = response.baseName;
-        // TODO(koz): Generate a persistent id in the browser and use it here.
-        var id = fileSystemId + ":" + baseName;
+        var id = response.id;
         var fs = GetIsolatedFileSystem(fileSystemId);
 
         try {
           // TODO(koz): fs.root.getFile() makes a trip to the browser process,
           // but it might be possible avoid that by calling
           // WebFrame::createFileEntry().
           fs.root.getFile(baseName, {}, function(fileEntry) {
             entryIdManager.registerEntry(id, fileEntry);
             callback(fileEntry);
           }, function(fileError) {
@@ skipping 31 matching lines @@
   };
 
   fileSystem.chooseFile = function() {
     console.log("chrome.fileSystem.chooseFile is deprecated");
     console.log("Please use chrome.fileSystem.chooseEntry instead");
     fileSystem.chooseEntry.apply(this, arguments);
   };
 });
 
 exports.binding = binding.generate();