Google-drive – How to reset permissions for Google Drive documents in all subfolders

I installed Vidar’s script and works very well for files, but wouldn't reset permissions on folders. So, I changed a little bit the code to make the folders also inherite the permissions from their upper folder.

Two important disclaimers:

1. I don't know if the original intention was to leave folders unchanged. Or even if it worked well for everybody but me, and this solutions was unnecesary. It worked for me.
2. This is the first script I do, so it is very likely that it is not very efficient and may content some errors. Please feel free to correct it and improve it.

I only changed the doResetPermissions function, but I paste all the code for simplicity reasons.

var selectedFolder;
var dialog;

function doGet() {
  var app = UiApp.createApplication();
  var heading = app.createHTML("<h1>Folders for</h1>");
  app.add(heading);
  var allFoldersIterator = DriveApp.getFolders();
  var text = app.createTextArea().setName("text").setId("output");
  app.add(text);
  var tree = app.createTree();
  var rootFolder = DriveApp.getRootFolder();
  var treeRoot = app.createTreeItem(rootFolder.getName()).setId(rootFolder.getId());
  var handler = app.createServerHandler("folderSelected");
  tree.addItem(treeRoot);
  tree.addSelectionHandler(handler);
  treeRoot.setState(true);
  createBranch(rootFolder, treeRoot, app);
  app.add(tree);
  var selectedFolderIdBox = app.createTextBox().setName("selectedFolderIdBox").setId("selectedFolderIdBox");
  app.add(selectedFolderIdBox);
  return app;
}

function createBranch(folder, branch, app) {
  var children = folder.getFolders();
  while (children.hasNext()) {
    child = children.next();
    Logger.log("Folder id: " + child.getId());
    var subBranch = app.createTreeItem(child.getName()).setId(child.getId());
    branch.addItem(subBranch);
    createBranch(child, subBranch, app);
  }
}

function folderSelected(eventInfo) {
  var app = UiApp.getActiveApplication();
  var parameter = eventInfo.parameter;
  Logger.log("Selected " + eventInfo.parameter.selected);
  selectedFolder = DriveApp.getFolderById(eventInfo.parameter.selected);
  var selectedFolderIdBox = app.getElementById("selectedFolderIdBox");
  selectedFolderIdBox.setValue(eventInfo.parameter.selected);
  var okHandler = app.createServerHandler("okResetPermissions");
  okHandler.addCallbackElement(selectedFolderIdBox);
  dialog = app.createDialogBox(true, true);
  var panel = app.createFlowPanel();
  dialog.add(panel);
  dialog.setId("confirmationDialog");
  dialog.setPopupPosition(100, 100).setSize(500, 500);
  panel.add(app.createLabel("Do you want to reset permissions for all files found in folder " + selectedFolder.getName() + " and its subfolders?\n (Click outside of the dialog box to cancel)"));
  panel.add(app.createButton("Do it!", okHandler));
  dialog.show();
  return app;
}

function okResetPermissions(eventInfo) {
  var selectedFolderId = eventInfo.parameter.selectedFolderIdBox;
  var selectedFolder = DriveApp.getFolderById(selectedFolderId);
  Logger.log("Resetting permissions on " + selectedFolder.getName());
  var app = UiApp.getActiveApplication();
  app.getElementById("confirmationDialog").hide();
  Logger.log("Confirmation dialog hidden");
  var progressIndicator = app.createDialogBox(false, true);
  progressIndicator.setId("progressIndicator");
  progressIndicator.setPopupPosition(100, 100).setSize(500, 500);
  var label = app.createLabel("Working ...");
  progressIndicator.add(label);
  progressIndicator.show();
  doResetPermissions(selectedFolder, function() {
    var app = UiApp.getActiveApplication();
    var progressIndicator = app.getElementById("progressIndicator");
    progressIndicator.hide();
    return app;
  });
  return app;
}

function doResetPermissions(selectedFolder, callback) {
  Logger.log("Resetting permissions on folder " + selectedFolder.getName());

  var sharingAccess = selectedFolder.getSharingAccess();
  var sharingPermission = selectedFolder.getSharingPermission();

  var viewersfolder = selectedFolder.getViewers();
  Logger.log("Number of Viewers in folder: " + selectedFolder.getName() + " = " + viewersfolder.length);
  for (var i = 0; i < viewersfolder.length; i++) {
    Logger.log("      Removing viewer " + viewersfolder[i].getEmail());
    selectedFolder.removeViewer(viewersfolder[i]);
  }

  var editorsfolder = selectedFolder.getEditors();

  Logger.log("Number of Editors in folder: " + selectedFolder.getName() + " = " + editorsfolder.length);

  for (var i = 0; i < editorsfolder.length; i++) {
    Logger.log("      Removing editor " + editorsfolder[i].getEmail());
    selectedFolder.removeEditor(editorsfolder[i]);
  }

  var files = selectedFolder.getFiles();
  while (files.hasNext()) {
    var file = files.next();
    Logger.log("   Resetting permissions on file " + file.getName());
    file.setSharing(sharingAccess, sharingPermission);

    var viewers = file.getViewers();
    Logger.log("Number of Viewers in file: " + file.getName() + " = " + viewers.length);
    for (var i = 0; i < viewers.length; i++) {
      Logger.log("      Removing viewer " + viewers[i].getEmail());
      file.removeViewer(viewers[i]);
    }

    var editors = file.getEditors();

    Logger.log("Number of editors in file: " + file.getName() + " = " + editors.length);

    for (var i = 0; i < editors.length; i++) {
      Logger.log("      Removing editor " + editors[i].getEmail());
      file.removeEditor(editors[i]);
    }
  }

  var children = selectedFolder.getFolders();
  while (children.hasNext()) {
    var child = children.next();
    doResetPermissions(child);
  }

  if (callback) {
    callback();
  }
}