Chrome Version       : 69.0.3497.81
URLs (if applicable) : about:
Other browsers tested: Chrome
  Add OK or FAIL, along with the version, after other browsers where you
have tested this issue:
     Chrome: OK (works when not in headless mode)

What steps will reproduce the problem?
(1) Install Selenium + Python + chromedriver
(2) Launch headless Chrome using Selenium w/ chromedriver
(3) Navigate to "about:" or "about:version"

What is the expected result?

  An immediate response.

What happens instead?

  Nothing ... the navigation sticks until timing out after about 5 minutes.

Please provide any additional information below. Attach a screenshot if
possible.

Here is some Python 2.7 code that reproduces the issue on two different Mac OS X machines:

from selenium import webdriver
options = webdriver.ChromeOptions()
options.add_argument('headless')
headless_chrome = webdriver.Chrome(chrome_options=options)
headless_chrome.get('about:')