Adjust leak detector expectations for IntersectionObserver

Adjust leak detector expectations for IntersectionObserver

If the root document registers an intersection observer, an
IntersectionObserverController (i.e., an ActiveDOMObject) will be
created for that document. Since the object also holds a reference to
the document, it will not be collected as long as the root document
is live. This can cause the leak detector to falsely conclude that a new
active DOM object is being leaked.

This patch avoids the problem by increasing the number of expected
active DOM objects in the leak detector.

BUG=661182

[Sami, 2016-11-11 15:21:58]

The CQ bit was checked by skyostil@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-11-11 15:22:14]

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

[Sami, 2016-11-11 15:23:34]

Description was changed from

==========
Adjust leak detector expectations for IntersectionObserver

If the root document registers an intersection observer, an
IntersectionObserverController (i.e., an ActiveDOMObject) will be
created for that document. Since the object also holds a reference to
the document, it will not be collected as long as the root document
is live. This can cause the leak detector to falsely conclude that a new
active DOM object is being leaked.

This patch avoids the problem by increasing the number of expected
active DOM objects in the leak detector.

BUG=661182
==========

to

==========
Adjust leak detector expectations for IntersectionObserver

If the root document registers an intersection observer, an
IntersectionObserverController (i.e., an ActiveDOMObject) will be
created for that document. Since the object also holds a reference to
the document, it will not be collected as long as the root document
is live. This can cause the leak detector to falsely conclude that a new
active DOM object is being leaked.

This patch avoids the problem by increasing the number of expected
active DOM objects in the leak detector.

BUG=661182
==========

[Sami, 2016-11-11 15:23:35]

skyostil@chromium.org changed reviewers:
+ hajimehoshi@chromium.org, sigbjorn@opera.com

[Sami, 2016-11-11 15:23:42]

PTAL.

[Sami, 2016-11-11 18:02:10]

The CQ bit was checked by skyostil@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-11-11 18:02:26]

Dry run: 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, 2016-11-11 18:32:24]

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

[commit-bot: I haz the power, 2016-11-11 18:32:25]

Dry run: This issue passed the CQ dry run.

[hajimehoshi, 2016-11-14 04:41:59]

hajimehoshi@chromium.org changed reviewers:
+ kouhei@chromium.org

[hajimehoshi, 2016-11-14 04:42:31]

On 2016/11/11 15:23:42, Sami wrote:
> PTAL.

This seems to affect all leak-detecting tests. Have you tested this on your
local machine?

[sof, 2016-11-14 10:59:07]

sigbjornf@opera.com changed reviewers:
+ sigbjornf@opera.com

[sof, 2016-11-14 10:59:08]

that's a good&valid point, unconditionally incrementing the count might hide a
single ActiveDOMObject leak elsewhere if IntersectionObservers aren't involved.

Might it be an idea to have the WebLeakDetector (and root Document)
configure/initialize the expected leak counts?

[hajimehoshi, 2016-11-14 11:50:33]

Sorry but I'm not fully understand the situation. The leak detector compares the
numbers of the objects before and after loading about:blank. Is this the case
that an IntersectionObserver lives even after loading about:blank in some cases?

[hajimehoshi, 2016-11-14 11:51:29]

s/I'm not fully understand/I don't fully understand/