Add Isolate::DiscardThreadSpecificMetadata method to embedder API.

Add Isolate::DiscardThreadSpecificMetadata method to embedder API.

If many threads use the same Isolate (or many Isolates) and then
terminate, their PerIsolateThreadData objects are never cleaned
up, resulting in a slow memory leak and, worse, the
PerIsolateThreadData chain getting larger and larger, adversely
affecting performance.

In this situation, embedders will now be encouraged to apply
DiscardThreadSpecificMetadata against any Isolate a thread is
done with, especially if the thread is about to terminate.

Note that it is harmless to run DiscardThreadSpecificMetadata
against an Isolate for which a thread has no thread data and
per-Isolate thread data can be reestablished if a thread starts
using an Isolate again after running DiscardThreadSpecificMetadata
against it.

It is, however, an embedder error to run
DiscardThreadSpecificMetadata against an Isolate in thread with a
Locker for the Isolate in the stack or against an Entered Isolate.

This change cannot cause any change in behavior in existing apps
as the only added coded can only be reached via the new
DiscardThreadSpecificMetadata method.

R=Jakob, jochen
BUG=

Committed: https://crrev.com/aeb8073c4a540010bb637d50790018041c5041c8
Cr-Commit-Position: refs/heads/master@{#32909}

[alexk, 2015-12-12 01:23:28]

Phew! My drunkard's walk finally succeeded in getting this issue under my work
e-mail address. Sorry if my flailing filled up your inbox.

[alexk, 2015-12-12 01:30:27]

The CQ bit was checked by akodat@rocketsoftware.com to run a CQ dry run

[commit-bot: I haz the power, 2015-12-12 01:30:38]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1522703002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1522703002/1

[commit-bot: I haz the power, 2015-12-12 01:30:39]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-12-12 01:30:40]

Dry run: No L-G-T-M from a valid reviewer yet. Only full committers are
accepted.
Even if an L-G-T-M may have been provided, it was from a non-committer,
_not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[jochen (gone - plz use gerrit), 2015-12-14 12:33:20]

https://codereview.chromium.org/1522703002/diff/1/AUTHORS
File AUTHORS (right):

https://codereview.chromium.org/1522703002/diff/1/AUTHORS#newcode31
AUTHORS:31: Rocket Software, Inc. <*@rocketsoftware.com>
hum, I can't find this entry in the list of CCLA signers (I could find your
gmail address, however, if you submit this code for rocketsofware.com, they also
need to sign the cla)

https://codereview.chromium.org/1522703002/diff/1/AUTHORS#newcode36
AUTHORS:36: Alex Kodat <akodat@rocketsoftware.com>
one entry is enough

[jochen (gone - plz use gerrit), 2015-12-16 08:22:54]

ok, the CLA stuff is sorted out now

can you remove the wildcard entry, so there are no duplications?

with that, this change lgtm

[alexk, 2015-12-16 13:11:46]

AUTHORS fixed up.

[jochen (gone - plz use gerrit), 2015-12-16 15:04:47]

The CQ bit was checked by jochen@chromium.org

[jochen (gone - plz use gerrit), 2015-12-16 15:04:47]

The patchset sent to the CQ was uploaded after l-g-t-m from jochen@chromium.org
Link to the patchset: https://codereview.chromium.org/1522703002/#ps20001
(title: "Remove rocketsoftware wildcard from AUTHORS")

[commit-bot: I haz the power, 2015-12-16 15:04:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1522703002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1522703002/20001

[commit-bot: I haz the power, 2015-12-16 15:49:32]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-12-16 15:49:57]

Description was changed from

==========
Add Isolate::DiscardThreadSpecificMetadata method to embedder API.

If many threads use the same Isolate (or many Isolates) and then
terminate, their PerIsolateThreadData objects are never cleaned
up, resulting in a slow memory leak and, worse, the
PerIsolateThreadData chain getting larger and larger, adversely
affecting performance.

In this situation, embedders will now be encouraged to apply
DiscardThreadSpecificMetadata against any Isolate a thread is
done with, especially if the thread is about to terminate.

Note that it is harmless to run DiscardThreadSpecificMetadata
against an Isolate for which a thread has no thread data and
per-Isolate thread data can be reestablished if a thread starts
using an Isolate again after running DiscardThreadSpecificMetadata
against it.

It is, however, an embedder error to run
DiscardThreadSpecificMetadata against an Isolate in thread with a
Locker for the Isolate in the stack or against an Entered Isolate.

This change cannot cause any change in behavior in existing apps
as the only added coded can only be reached via the new
DiscardThreadSpecificMetadata method.

R=Jakob, jochen
BUG=
==========

to

==========
Add Isolate::DiscardThreadSpecificMetadata method to embedder API.

If many threads use the same Isolate (or many Isolates) and then
terminate, their PerIsolateThreadData objects are never cleaned
up, resulting in a slow memory leak and, worse, the
PerIsolateThreadData chain getting larger and larger, adversely
affecting performance.

In this situation, embedders will now be encouraged to apply
DiscardThreadSpecificMetadata against any Isolate a thread is
done with, especially if the thread is about to terminate.

Note that it is harmless to run DiscardThreadSpecificMetadata
against an Isolate for which a thread has no thread data and
per-Isolate thread data can be reestablished if a thread starts
using an Isolate again after running DiscardThreadSpecificMetadata
against it.

It is, however, an embedder error to run
DiscardThreadSpecificMetadata against an Isolate in thread with a
Locker for the Isolate in the stack or against an Entered Isolate.

This change cannot cause any change in behavior in existing apps
as the only added coded can only be reached via the new
DiscardThreadSpecificMetadata method.

R=Jakob, jochen
BUG=

Committed: https://crrev.com/aeb8073c4a540010bb637d50790018041c5041c8
Cr-Commit-Position: refs/heads/master@{#32909}
==========

[commit-bot: I haz the power, 2015-12-16 15:49:58]

Patchset 2 (id:??) landed as
https://crrev.com/aeb8073c4a540010bb637d50790018041c5041c8
Cr-Commit-Position: refs/heads/master@{#32909}