To support passing the window object to the onShown event, we need the frameID of the tab content.
<rdar://problem/88383984>
Created attachment 450659 [details] Patch
Comment on attachment 450659 [details] Patch r=me
Committed r288999 (246717@main): <https://commits.webkit.org/246717@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 450659 [details].