Require visibility & focus at the point of consuming "transient activation"

[jan-ivar]

While reviewing screen-capture I found folks who assumed having a "user gesture" implicitly guaranteed a page was visible and focused.

Such thinking may come from earlier implementations, which in contrast to the timer-based transient activation perhaps were rooted in tracking the callstack of the executing JS back to some event handler blessed by being triggered by the end user interacting with the page.

Even though this may never have been 100% guaranteed (implementations carrying this blessing across promises etc), this nevertheless seems like a reasonable guarantee to enforce. cc @annevk @youennf

[domenic]

@mustaqahmed WDYT?

[marcoscaceres]

Ran into this also in the Screen Orientation API. Although it's a hypothetical scenario, I think it's a reasonable check to add (at least, the visibility check... not sure about the focused part).