Bypassing Cloudflare Scrapeshield
See, what scrapeshield does is checking if you are using a real browser, it's essentially checking your browser for certain bugs in them. Let's say that Chrome can't process an IFrame if there is a 303 error in the line at the same time, certain web browser react differently to different tests, so webdriver must not react to these causing the system to say "We got an intruder, change the page!". I might be correct, not 100% sure though...
More Info on source:
I found most of this information on a Defcon talk about web sniffers and preventing them from getting the proper vulnerability information on the server, he made a web browser identifier in PHP too.