Actions menu autofocus on elements doesn't work initially

[PVince81]

Steps

1. Tested in the Talk app
2. Focus on the new message form
3. Use shift+tab to tab up to the three dots menu.
4. Hit enter, then try to move up and down with the keyboard.

Expected result

Able to move up/down

Actual result

The item is not focussed.
Querying document.activeElement shows that the focus is still on the trigger.

Opening the menu a second time makes the issue disappear.

This is because the first render of the popover doesn't become visible directly and has an arbitrary delay defined by requestAnimationFrame, see my upstream report for details: Akryum/floating-vue#661

Workaround

Depending whether upstream will accept a PR that emits a new event or not, there are other possible workarounds:

1. Extend our Popover component to monitor the DOM periodically in the @show handler, and only once the .open class appears, trigger another event like afterShow. Only do so if there's a handler set there.
2. Like 1 but do the periodic monitoring in the Actions class
3. Like 2 but simply retry focussing the first element if it failed

So far I prefer approach 1 as a temporary workaround until v-tooltip is fixed upstream.

[PVince81]

no need to monitor the DOM, I managed to make it work by watching this.$refs.popover.isOpen

PR here: #1761