Add support for persistent file access in apps.

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 fileSystemNatives = requireNative('file_system_natives');
 var forEach = require('utils').forEach;
 var GetIsolatedFileSystem = fileSystemNatives.GetIsolatedFileSystem;
 var lastError = require('lastError');
+var sendRequest = require('sendRequest').sendRequest;
 var GetModuleSystem = requireNative('v8_context').GetModuleSystem;
 // TODO(sammc): Don't require extension. See http://crbug.com/235689.
 var GetExtensionViews = requireNative('extension').GetExtensionViews;
 
 var backgroundPage = GetExtensionViews(-1, 'BACKGROUND')[0];
 var backgroundPageModuleSystem = GetModuleSystem(backgroundPage);
 var entryIdManager = backgroundPageModuleSystem.require('entryIdManager');
 
 // All windows use the bindFileEntryCallback from the background page so their
 // FileEntry objects have the background page's context as their own. This
@@ skipping 51 matching lines @@
     apiFunctions.setUpdateArgumentsPostValidate(
         functionName, function(fileEntry, callback) {
       var fileSystemName = fileEntry.filesystem.name;
       var relativePath = fileEntry.fullPath.slice(1);
       return [fileSystemName, relativePath, callback];
     });
   }
   forEach(['getDisplayPath', 'getWritableEntry', 'isWritableEntry'],
           bindFileEntryFunction);
 
-  forEach(['getWritableEntry', 'chooseEntry'], function(i, functionName) {
+  forEach(['getWritableEntry', 'chooseEntry', 'restoreEntry'],
+      function(i, functionName) {
     bindFileEntryCallback(functionName, apiFunctions);
   });
 
-  apiFunctions.setHandleRequest('getEntryId', function(fileEntry) {
-    return entryIdManager.getEntryId(fileEntry);
+  apiFunctions.setHandleRequest('retainEntry', function(fileEntry) {
+    var id = entryIdManager.getEntryId(fileEntry);
+    if (!id)
+      return '';
+    var fileSystemName = fileEntry.filesystem.name;
+    var relativePath = fileEntry.fullPath.slice(1);
+
+    sendRequest(this.name, [id, fileSystemName, relativePath],
+      this.definition.parameters, {});
+    return id;
   });
 
-  apiFunctions.setHandleRequest('getEntryById', function(id) {
-    return entryIdManager.getEntryById(id);
+  apiFunctions.setHandleRequest('isRestorable',
+      function(id, callback) {
+    var savedEntry = entryIdManager.getEntryById(id);
+    if (savedEntry) {
+      callback(true);
+    } else {
+      sendRequest(this.name, [id, callback], this.definition.parameters, {});
+    }
+  });
+
+  apiFunctions.setUpdateArgumentsPostValidate('restoreEntry',
+      function(id, callback) {
+    var savedEntry = entryIdManager.getEntryById(id);
+    if (savedEntry) {
+      callback(savedEntry);
+      return [id, false, null];
+    } else {
+      return [id, true, callback];
+    }
   });
 
   // TODO(benwells): Remove these deprecated versions of the functions.
   fileSystem.getWritableFileEntry = function() {
     console.log("chrome.fileSystem.getWritableFileEntry is deprecated");
     console.log("Please use chrome.fileSystem.getWritableEntry instead");
     fileSystem.getWritableEntry.apply(this, arguments);
   };
 
   fileSystem.isWritableFileEntry = function() {
     console.log("chrome.fileSystem.isWritableFileEntry is deprecated");
     console.log("Please use chrome.fileSystem.isWritableEntry instead");
     fileSystem.isWritableEntry.apply(this, arguments);
   };
 
   fileSystem.chooseFile = function() {
     console.log("chrome.fileSystem.chooseFile is deprecated");
     console.log("Please use chrome.fileSystem.chooseEntry instead");
     fileSystem.chooseEntry.apply(this, arguments);
   };
 });
 
 exports.bindFileEntryCallback = bindFileEntryCallback;
 exports.binding = binding.generate();