Scrolling with 60fps
In the frames section of Chrome Developer Tools, we can inspect how smooth things appear on the screen while browsing a website. This is a useful tool that allows us to test the responsiveness of a site in regard to loading, scripting, rendering and painting. Recording a browser session allows us to see the frames as they appear. Then we can easily compare if we reach the target of 60fps. 60fps might seem quite much for a website, if we consider that our eye won't object while watching a film or animation encoded with 30fps. Although a film can have a lot of action, it is still presented in a fixed amount of frames per second. A website has a more dynamic nature and we can't guarantee that every visitor will look at it in exactly the same way or that he/she will use similarly. A user can potentially turn on/off website components, rearrange things on the screen, download resources, or even juggle between Photoshop, Dreamweaver and Maya with his/her browser accidentally open. Every operation the PC performs affects the browsing experience directly or indirectly, which means that the results of measuring frames-per-second can vary greatly.
That said, I am a bit concerned that we might start looking at websites as animations and evaluate them from an fps standpoint rather than from a value standpoint. Even if animations are of high-bandwidth nature and can carry a lot of information, there are far too many situations where static content makes more sense. The truth is that both types usually complement each other. So we probably can't measure a site from a single perspective and simply label it “jank-free”. Scrolling moves content up and down so we see it animated, but it's usually not where most of the user's time is spent, since it temporary blocks other kinds of interactions with the page. It's not the main mode of operation on a website to be measured in that way. How important could be to scroll with 60fps if the user can't do anything else?