Problem: A navigation could intermittently hang forever with no load
event ever firing. In test-web, that surfaced as a 120-second
“pre-navigation timeout, WebContent process may be unresponsive”: The
about:blank load used for clearing the document between tests would
never complete — leaving WebContent idle while the harness waited.
Cause: begin_navigation claims the navigable’s ongoing navigation id and
then awaits an asynchronous unload check. While it waits, a session-
history traversal can re-stamp the navigable’s ongoing navigation to
“traversal”. When the unload check resumes, the navigation finds that
its ongoing navigation ID no longer matches — and silently aborts. But
nothing ever re-runs it — so the navigation is lost. The deferral guard
at the top of begin_navigation, which defers a navigation while a
traversal is already ongoing, runs before this window — so a traversal
that begins during the unload check slips past it.
Fix: When the post-unload-check guard finds the navigable is now running
a traversal, re-defer the navigation into the pending navigations list
instead of dropping it — mirroring the existing deferral guard. Clearing
the ongoing traversal drains the pending navigations — so the navigation
runs to completion as a fresh attempt once the traversal finishes.
Fixes https://github.com/LadybirdBrowser/ladybird/issues/10122.
e918a448e4