The latter is a feature of Microsoft’s Visual Studio developer tools that measures how users interact with an application. The most often used functions are then optimized by PGO, sometimes increasing their binary size, and optimizing the memory location of the browser code so that those functions can be kept in the CPU’s fast instruction cache.
PGO was implemented first with the Chrome 53 release of 64-bit Chrome, followed by version 54 of 32-bit Chrome. Google claims it’s seen startup times improved by 17%, new tab page load times by almost 15%, and overall page load times by 6%.
You can read more about how PGO works in here.
In related news, Google is currently testing a usability-focused design change in the Canary release of Chrome for Android that moves moves the search bar to the bottom of the screen. The change currently has to be manually enabled through a Chrome flag and is intended to improve one hand use for people with large smartphones.