Use the LibWebView history mirror to preserve traversable session
history across WebContent process swaps. WebContent reports snapshots to
the UI process, and new renderers can be seeded from the mirror.
Browser back and forward now resolve through the UI-owned used history
steps. WebContent still runs the spec traversal path when the current
renderer has enough matching state to do so.
Handle canceled and no-op UI navigations without leaving speculative
history entries or pending WebDriver waits behind. Preserve traversal
precheck state across synchronous IPC shutdown, and avoid overwriting a
restored target entry's persisted scroll state before the document has
adopted that entry.
Enable -Wexit-time-destructors for all in-tree library targets and
update process-lifetime library statics so they no longer register
exit-time destructors. Long-lived caches, lookup tables, singleton
registries, and generated constants now use NeverDestroyed or leaked
references where the data is intended to live until process exit.
Update LibWeb, LibLine, and the binding generators so regenerated
sources follow the same rule instead of reintroducing destructed
statics.
Lots of editorial spec bugs here, but these changes largely affect how
the unhandledPromptBehavior capability is handled. We also now set an
additional capability for the default User Agent string.
WebDriver script authors may now provide either:
* A user prompt handler configuration to be used for all prompt types.
* A set of per-prompt-type user prompt handlers.
This also paves the way for interaction with the beforeunload prompt,
though we do not yet support that feature in LibWeb.
See: https://github.com/w3c/webdriver/commit/43903d0
