Anecdotally, I notice that tab switching is slow. I frequently use ctr + tab to move between tabs. Sometimes, there's a noticeable delay before the tab switches. 

I don't have exact details - haven't been paying too much attention.

I suspect what's happening is that there's nothing to display for the web contents and it will be a long time before anything is available to display. Tab discarding? Something else? We end up waiting for a timeout on the UI thread, which we end up hitting, and then switching to the tab anyways. Seems worse than just switching to the tab and waiting for contents to display.