Tracing HeapListHashSet<> iterators.

Tracing HeapListHashSet<> iterators.

The HeapListHashSet<> iterators keep a pair of heap references, which
really should be traced like any other such reference during GCs. This
isn't unsafe for the stack allocated uses of these iterators, but one
Blink object (CSSSegmentedFontFace) keeps an iterator as a field on the
heap, we really have to trace these on-heap part object iterators.

Add the needed infrastructure and use it for CSSSegmentedFontFace.

R=haraken
BUG=672030
Committed: https://crrev.com/de25fdc5de7ddb6353360e9424cef0792d70587e
Cr-Commit-Position: refs/heads/master@{#439748}

[sof, 2016-12-19 22:10:16]

The CQ bit was checked by sigbjornf@opera.com to run a CQ dry run

[commit-bot: I haz the power, 2016-12-19 22:11:05]

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

[sof, 2016-12-19 22:27:17]

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

[sof, 2016-12-19 22:27:17]

please take a look.

The only "on heap" iterator in Blink; its untraced references do not represent a
problem today (with or without heap compaction), but it's preferable to let the
GC know about them.

[commit-bot: I haz the power, 2016-12-20 01:43:18]

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

[commit-bot: I haz the power, 2016-12-20 01:43:19]

Dry run: This issue passed the CQ dry run.

[haraken, 2016-12-20 02:53:05]

haraken@chromium.org changed reviewers:
+ haraken@chromium.org

[haraken, 2016-12-20 02:53:05]

LGTM

https://codereview.chromium.org/2583363002/diff/1/third_party/WebKit/Source/w...
File third_party/WebKit/Source/wtf/ListHashSet.h (right):

https://codereview.chromium.org/2583363002/diff/1/third_party/WebKit/Source/w...
third_party/WebKit/Source/wtf/ListHashSet.h:665: m_iterator.trace(visitor);

Just to confirm: This iterator is just pointing to a Node of ListHashSet and not
pointing to anything middle in a backing storage, right?

[sof, 2016-12-20 06:37:09]

https://codereview.chromium.org/2583363002/diff/1/third_party/WebKit/Source/w...
File third_party/WebKit/Source/wtf/ListHashSet.h (right):

https://codereview.chromium.org/2583363002/diff/1/third_party/WebKit/Source/w...
third_party/WebKit/Source/wtf/ListHashSet.h:665: m_iterator.trace(visitor);
On 2016/12/20 02:53:05, haraken wrote:
> 
> Just to confirm: This iterator is just pointing to a Node of ListHashSet and
not
> pointing to anything middle in a backing storage, right?
> 

Yes, the nodes in this list are separately allocated, which the backing store
then keeps pointers to, for faster access than the linked view. The iterator
refers to the current node + the ListHashSet<> itself for when it needs to get
at the head/tail of the list.

[sof, 2016-12-20 08:07:39]

Description was changed from

==========
Tracing HeapListHashSet<> iterators.

The HeapListHashSet<> iterators keep a pair of heap references, which
really should be traced like any other such reference during GCs. This
isn't unsafe for the stack allocated uses of these iterators, but one
Blink object (CSSSegmentedFontFace) keeps an iterator as a field on the
heap, we really have to trace these on-heap part object iterators.

Add the needed infrastructure and use it for CSSSegmentedFontFace.

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

to

==========
Tracing HeapListHashSet<> iterators.

The HeapListHashSet<> iterators keep a pair of heap references, which
really should be traced like any other such reference during GCs. This
isn't unsafe for the stack allocated uses of these iterators, but one
Blink object (CSSSegmentedFontFace) keeps an iterator as a field on the
heap, we really have to trace these on-heap part object iterators.

Add the needed infrastructure and use it for CSSSegmentedFontFace.

R=haraken
BUG=672030
==========

[sof, 2016-12-20 08:07:53]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2016-12-20 08:08:06]

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, 2016-12-20 08:14:03]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1482221273578540, "parent_rev":
"927351d738bbc573f50c1f224674a1eece47a6d8", "commit_rev":
"63c20172b8f2018e548846f51c9b6ee258db032f"}

[commit-bot: I haz the power, 2016-12-20 08:14:29]

Description was changed from

==========
Tracing HeapListHashSet<> iterators.

The HeapListHashSet<> iterators keep a pair of heap references, which
really should be traced like any other such reference during GCs. This
isn't unsafe for the stack allocated uses of these iterators, but one
Blink object (CSSSegmentedFontFace) keeps an iterator as a field on the
heap, we really have to trace these on-heap part object iterators.

Add the needed infrastructure and use it for CSSSegmentedFontFace.

R=haraken
BUG=672030
==========

to

==========
Tracing HeapListHashSet<> iterators.

The HeapListHashSet<> iterators keep a pair of heap references, which
really should be traced like any other such reference during GCs. This
isn't unsafe for the stack allocated uses of these iterators, but one
Blink object (CSSSegmentedFontFace) keeps an iterator as a field on the
heap, we really have to trace these on-heap part object iterators.

Add the needed infrastructure and use it for CSSSegmentedFontFace.

R=haraken
BUG=672030

Review-Url: https://codereview.chromium.org/2583363002
==========

[commit-bot: I haz the power, 2016-12-20 08:14:30]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-12-20 08:18:29]

Description was changed from

==========
Tracing HeapListHashSet<> iterators.

The HeapListHashSet<> iterators keep a pair of heap references, which
really should be traced like any other such reference during GCs. This
isn't unsafe for the stack allocated uses of these iterators, but one
Blink object (CSSSegmentedFontFace) keeps an iterator as a field on the
heap, we really have to trace these on-heap part object iterators.

Add the needed infrastructure and use it for CSSSegmentedFontFace.

R=haraken
BUG=672030

Review-Url: https://codereview.chromium.org/2583363002
==========

to

==========
Tracing HeapListHashSet<> iterators.

The HeapListHashSet<> iterators keep a pair of heap references, which
really should be traced like any other such reference during GCs. This
isn't unsafe for the stack allocated uses of these iterators, but one
Blink object (CSSSegmentedFontFace) keeps an iterator as a field on the
heap, we really have to trace these on-heap part object iterators.

Add the needed infrastructure and use it for CSSSegmentedFontFace.

R=haraken
BUG=672030

Committed: https://crrev.com/de25fdc5de7ddb6353360e9424cef0792d70587e
Cr-Commit-Position: refs/heads/master@{#439748}
==========

[commit-bot: I haz the power, 2016-12-20 08:18:30]

Patchset 1 (id:??) landed as
https://crrev.com/de25fdc5de7ddb6353360e9424cef0792d70587e
Cr-Commit-Position: refs/heads/master@{#439748}