I was under the assumption that Googlebot already used a headless Chrome to index websites for some time.
Google used Chrome to generated page preview pictures (at index-time) to show the search terms (mouse over, but this feature is no more, as it seems). Some websites that shows you the user agent displayed the Chrome user-agent in the preview picture, back then (~2 years ago).
I've heard speculation that this is a large reason why Google invests so heavily in Chrome. When developers make their sites work with Chrome, they end up making their sites work nicely for the Googlebot without even realizing it.
If the Googlebot used a web engine that wasn't found in a common browser, then they would have to pay the costs to make it compatible with all web pages out there. Instead, they push that cost onto developers targeting Chrome. All work to make websites work right in Chrome also make them work for the Googlebot, effectively standardizing the web onto something that the Googlebot knows how to process.
I always thought this was the secret reason Chrome was built. Build a better Googlebot and then, wait a minute, why not just release an awesome browser to get more people using our product at the same time? Forked.
Technically speaking, Google built the new Googlebot and then realized that they could release parts of Googlebot to the public in the form of a web browser.
I was glad when instant preview was released. I would always somehow accidentally mouse over the preview area and get stuck with a random site showing up on half my screen. Terrible UX.
Google used Chrome to generated page preview pictures (at index-time) to show the search terms (mouse over, but this feature is no more, as it seems). Some websites that shows you the user agent displayed the Chrome user-agent in the preview picture, back then (~2 years ago).
it was called Instant Preview: http://googlesystem.blogspot.co.at/2010/11/google-instant-pr...
details: https://sites.google.com/site/webmasterhelpforum/en/faq-inst...
Google removed this useful feature in 04/2013 :(
-- https://productforums.google.com/forum/#!topic/websearch/Aom...