ChromeDriver/Selenium exception when enumerating sessions that include Service Workers

See http://goo.gl/ll2FvQ for common issues.

Issue Description:

A Service Worker is a new kind of Web Worker. When ChromeDriver is driving a 
page that uses one of these, it raises an exception like:

  File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/errorhandler.py", line 166, in check_response
    raise exception_class(message, screen, stacktrace)
WebDriverException: Message: u'unknown error: DevTools returned unknown 
type:service_worker\n  (Session info: chrome=40.0.2181.0)\n  (Driver info: 
chromedriver=2.10.267518,platform=Linux 3.13.0-36-generic x86_64)' 

Steps to reproduce (if relevant, you MUST provide a simplified html page or
link to public site):

1. Get (or build) Chrome 40
2. Set up Selenium to run it with --enable-experimental-web-platform-features
3. driver.get('http://jakearchibald.github.io/trained-to-thrill/')

-----Other helpful tips:
Attach your chromedriver log with verbose logging enabled (see
http://goo.gl/5Sx8mC for how to do this).

*I have a log* but this page says "Issue attachment storage quota exceeded."

Original issue reported on code.google.com by dominicc@google.com on 7 Oct 2014 at 7:22

ericmckean / chromedriver

ChromeDriver/Selenium exception when enumerating sessions that include Service Workers #920