Completely clear weak persistent references.

Completely clear weak persistent references.

If weak processing determines that a WeakPersistent<T> is now pointing
to an otherwise unreferenced object, clear out and deallocate its
underlying PersistentNode.

We previously would only clear the persistent reference, but keep the
PersistentNode. This would lead to imprecise counts of live persistents,
potentially triggering false asserts of leaking persistents during thread
termination GCs.

R=
BUG=

Committed: https://crrev.com/0508bde56b8a90655708fbd89418650f828ee546
Cr-Commit-Position: refs/heads/master@{#401880}

[sof, 2016-06-24 14:09:13]

sigbjornf@opera.com changed reviewers:
+ oilpan-reviews@chromium.org

[sof, 2016-06-24 14:09:13]

please take a look.

[haraken, 2016-06-24 14:32:30]

LGTM

[sof, 2016-06-24 14:37:35]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2016-06-24 14:37:54]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-06-24 16:35:28]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2016-06-24 16:37:19]

Description was changed from

==========
Completely clear weak persistent references.

If weak processing determines that a WeakPersistent<T> is now pointing
to an otherwise unreferenced object, clear out and deallocate its
underlying PersistentNode.

We previously would only clear the persistent reference, but keep the
PersistentNode. This would lead to imprecise counts of live persistents,
potentially triggering false asserts of leaking persistents during thread
termination GCs.

R=
BUG=
==========

to

==========
Completely clear weak persistent references.

If weak processing determines that a WeakPersistent<T> is now pointing
to an otherwise unreferenced object, clear out and deallocate its
underlying PersistentNode.

We previously would only clear the persistent reference, but keep the
PersistentNode. This would lead to imprecise counts of live persistents,
potentially triggering false asserts of leaking persistents during thread
termination GCs.

R=
BUG=

Committed: https://crrev.com/0508bde56b8a90655708fbd89418650f828ee546
Cr-Commit-Position: refs/heads/master@{#401880}
==========

[commit-bot: I haz the power, 2016-06-24 16:37:20]

Patchset 4 (id:??) landed as
https://crrev.com/0508bde56b8a90655708fbd89418650f828ee546
Cr-Commit-Position: refs/heads/master@{#401880}