Use headless chromium with capybara and selenium webdriver - today!

UPDATE: we have a new version of this post out that resolves some of the gotchas below.

Here's a Rubyist's magic incantation to run headless chromium with selenium-webdriver and capybara: (it will be similar in other languages)

require 'selenium-webdriver'

Capybara.register_driver :headless_chromium do |app|
  caps = Selenium::WebDriver::Remote::Capabilities.chrome(
    "chromeOptions" => {
      'binary' => '/home/myuser/chrome-linux-440004/chrome',
      'args' => ['headless', 'disable-gpu']
    }
  )
  driver = Capybara::Selenium::Driver.new(
    app,
    browser: :chrome,
    desired_capabilities: caps
  )
end

Hints

1. You need a chromium (chrome) binary that reports version 57 (version 59 is too new). For example, snapshot 440004 - just download and unzip.
2. You need a recent chromedriver binary with support for headless chrome. For example, snapshot 460342 - just download and unzip.
3. If you get the error unrecognized chrome version, then see (1) above - you probably have a too-recent chromium.

Thanks to @dkastner!