Chrome support is through the platform specific ChromeDriver binary, which you download and put on your path.

b = :chrome

Chrome Preferences

prefs = {
  :download => {
    :prompt_for_download => false,
    :default_directory => "/path/to/dir"

b = :chrome, :prefs => prefs

See the full list of profile options here.

Chrome Switches

b = :chrome, :switches => %w[--ignore-certificate-errors --disable-popup-blocking --disable-translate]

See the full list of switches here.

Using a proxy with Chrome

b = :chrome, :switches => %w[]