This page focuses the first link below, clicks it, navigates to a second
page, then returns with history.back(). On restore it checks
whether document.activeElement is back on the original link.
The sampler installs an unload handler to force the navigation
down the non-BFCache path, matching the Chromium browser test more closely.
Note: on an unpatched browser, FAIL means the issue was
reproduced successfully. A fixed browser should report
activeElementAfterRestore: "target".
No run yet.