Bug 1355588 and bug 1355589 had been filed to track the new tab open/close animations, but just those two bugs won't be enough to track all the work needed here.
Since there has already been UX and engineering work on them, instead of converting one of them to a meta bug, I'm creating this new meta bug to track all the remaining work.
There are two parallel goals for investigating the creating of these new animations:
- visual refresh of these animations, continuing from the photon work
- improve their performance by running them off the main thread