Add cookie and session support to Dropbox file browser example.

app-configure-block.js

app.configure(function() {
  app.use(express.logger());
  app.use(express.bodyDecoder());
  app.use(express.cookieDecoder()); // Cookie-decoding.
  app.use(express.session());       // Session-handling.
});

file_browser-route.js

// File browser page.
app.get('/file_browser(/*)?', function(req, res) {
  // Fetch target metadata and render the page.
  if (req.session.dropbox) {
    req.session.dropbox.getMetadata(req.params[1] || '',
                                    function(err, metadata) {
      if (err) console.log('Error: ' + sys.inspect(err));
      else {
        res.render('file_browser.jade', {
          locals: {
            title: 'Dropbox File Browser',
            current_dir: (metadata.path.length > 0) ? metadata.path : 'root',
            items: metadata.contents
          }
        });
      }
    });
  } else res.redirect('home');
});

process_creds.js

// Upon response, extract access token/secret and redirect to file_browser.
request.on('response', function(token_res) {
  token_res.setEncoding('utf8');
  token_res.on('data', function(chunk) {
    var token_res = JSON.parse(chunk),
        access_token = token_res['token'],
        access_token_secret = token_res['secret'];
    req.session.dropbox = new DropboxClient(oauth, access_token,
                                            access_token_secret);
    res.redirect('/file_browser');
  });
});

remove-persistant-var-init.js

// Set up persistent variables.
// Delete this section or comment out the following line.
//var access_token = '', access_token_secret = '', dropbox = null;