Treat pending session history entries as absent from the used step
graph, and share that through a small step_value() helper so
snapshotting, Navigation API entry construction, target-entry lookup,
and forward clearing do not drift apart.
Keep cross-document history application tied to the navigation id that
created it. Queued changing-navigable work now finishes without
applying when a later navigation has already replaced its target, and
any traversal sentinel is cleared through the shared setter so queued
navigations can drain.
When navigation arrives while traversal is still ongoing, keep only the
newest pending navigation. This matches Chromium, WebKit, and Gecko on
sites that click through product or category links while prior loads
settle.
Revalidate queued same-document child continuations before running them
from null-document tasks, so removed frames or frames claimed by newer
navigations do not receive stale history state.
Preserve nested-history descriptors even when all child entries are
pending, keeping live child navigable identity available for later UI
process history seeds.
Add regression coverage for iframe renavigation during history commit,
for pending child history followed by a real navigation, and for removed
iframes with queued history updates.
394312ab5a