Applies the page's setting. Cheap and idempotent; turning it on starts the (lazy) enabling.
Removes the rasterizer this hook registered.
Resolves once the setting has taken effect, so a session is not minted before the rasterizer is registered. Never rejects.
Whether a capturer is registered and the preference is on (channels can offer pixels).
Owns the page's
frame-capturepreference for one widget.