That is quoted from the blog of google.

Site speed is one factor of SEO. It has been announced here:
Official Google Webmaster Central Blog: Using site speed in web search ranking

There are several ways to check the site speed, such as
Page Speed
YSlow
WebPagetest
Webmaster Tools

But recently, there is a new feature in Analytic to check the site speed.
It is available in new Google Analytic Beta. You need to
obtain the Beta dashboard and make a small change on
the tracking code on your website.

More details here: Google Analytics Blog: Measure Page Load Time
with Site Speed Analytics Report