commit ac59f66a2fd9d9898a787c26766c66bb01c8ea88
author Scott Haseley <shaseley@chromium.org> Mon Jan 05 21:05:43 2026
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Mon Jan 05 21:05:43 2026
tree 5d39f6d0a4415cf79a355d92c751ced4544c7e35
parent bd200494843c433a72271d97f6811ef7220b7190

Reland "[soft navs] Use a prefinalizer instead of UntracedMember for SoftNavigationContext"

This is a reland of commit 44f6a765b0170c296e5a61d9ed2e221b9e404138

The reland removes the always-failing Contains check called from the
prefinalizer [1], since it isn't needed with how we're currently
shutting down contexts. It also improves one of the GC tests, adding a
histogram expectation.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/7256268/comment/4b3c1f8b_e8f4eab8/

Original change's description:
> [soft navs] Use a prefinalizer instead of UntracedMember for SoftNavigationContext
>
> SoftNavigationHeuristics does custom tracing of the set of contexts
> using UntracedMember. This used to be how we detect the set becoming
> empty, but we don't track this any longer. We do still, however, record
> some metrics and end a trace event, so I think we still need detect
> when soft nav contexts are disposed.
>
> This CL changes how we do this to use a prefinalizer instead, which is
> generally preferred to UntracedMember. This is being done to make set
> iteration safer, since HashSet entry erasure invalidates iterators,
> which would be a problem if a set interaction causes a GC, e.g. due to
> an allocation. This is a prerequisite for crrev.com/c/7120640, where I
> don't trust that an iteration I need to add is safe.
>
> Bug: 454082771, 454082773
> Change-Id: Id7932cf4f12f838c588aaf559053421bb494235a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7256268
> Commit-Queue: Scott Haseley <shaseley@chromium.org>
> Reviewed-by: Michal Mocny <mmocny@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1559010}

Bug: 454082771, 454082773
Change-Id: I7829a6d37749ece49ce82a3ae71ee55e839cf5c9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7275266
Commit-Queue: Scott Haseley <shaseley@chromium.org>
Reviewed-by: Michal Mocny <mmocny@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1564582}