I think that not just google released its JS engines, which is at this stage almost the fastest and optimized for x86. Perhaps this is done in order to test it using google-chrome and then "add" it to your search analyzer sites. For this, JS processing speed is a very important and necessary thing.
If my guess is correct, google will soon please us with a search for pages generated using JS :). As a result, it should remove many of the “JS prohibitions” and the headache of AJAX developers.