Allow lazy removal of (context) lifecycle observers while stopping.

Allow lazy removal of (context) lifecycle observers while stopping.

r402141 imposed the restriction on ContextLifecycleObservers behavior
during stop() notifications of no longer being allowed to remove
observers while handling stop(). That constraint enables iteration
to be handled without allocating a snapshot of the observer set.

That restriction proves too constraining for media elements indirectly
holding onto AssociatedURLLoader objects while being stopped
(see associated bug for info.) Consequently, we allow observer removals
while keeping observer set iteration safe & allocation-free -- removals
are recorded while iterating, and removed in one go afterwards.

This is only done for notifyStoppingActiveDOMObjects(), as the other
notifications over context lifecycle observers do not require this
flexibility.

R=
BUG=623755
Committed: https://crrev.com/651bd9f00d9138c0118e9aa923b389d51bb33763
Cr-Commit-Position: refs/heads/master@{#402445}

[sof, 2016-06-28 08:42:08]

Description was changed from

==========
Allow lazy removal of (context) lifecycle observers while stopping.

r402141 imposed the restriction on ContextLifecycleObservers behavior
during stop() notifications of no longer being allowed to remove
observers while handling stop(). That constraint enables iteration
to be handled without allocating a snapshot of the observer set.

That restriction proves too constraining for media elements indirectly
holding onto AssociatedURLLoader objects while being stopped
(see associated bug for info.) Consequently, we allow observer removals
while keeping observer set iteration safe & allocation-free -- removals
are recorded while iterating, and removed in one go afterwards.

This is only done notifyStoppingActiveDOMObjects(), as the other
notifications over context lifecycle observers do not require this
flexibility.

R=
BUG=623755
==========

to

==========
Allow lazy removal of (context) lifecycle observers while stopping.

r402141 imposed the restriction on ContextLifecycleObservers behavior
during stop() notifications of no longer being allowed to remove
observers while handling stop(). That constraint enables iteration
to be handled without allocating a snapshot of the observer set.

That restriction proves too constraining for media elements indirectly
holding onto AssociatedURLLoader objects while being stopped
(see associated bug for info.) Consequently, we allow observer removals
while keeping observer set iteration safe & allocation-free -- removals
are recorded while iterating, and removed in one go afterwards.

This is only done for notifyStoppingActiveDOMObjects(), as the other
notifications over context lifecycle observers do not require this
flexibility.

R=
BUG=623755
==========

[sof, 2016-06-28 09:42:41]

sigbjornf@opera.com changed reviewers:
+ haraken@chromium.org

[sof, 2016-06-28 09:42:42]

please take a look.

[haraken, 2016-06-28 10:05:55]

LGTM (though I really want to remove code that removes observers while
iterating).

[sof, 2016-06-28 10:39:32]

On 2016/06/28 10:05:55, haraken wrote:
> LGTM (though I really want to remove code that removes observers while
> iterating).

Agreed,
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/web/Associated...
covers why we're in this situation here.

[sof, 2016-06-28 11:15:44]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2016-06-28 11:16:01]

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, 2016-06-28 12:19:43]

Description was changed from

==========
Allow lazy removal of (context) lifecycle observers while stopping.

r402141 imposed the restriction on ContextLifecycleObservers behavior
during stop() notifications of no longer being allowed to remove
observers while handling stop(). That constraint enables iteration
to be handled without allocating a snapshot of the observer set.

That restriction proves too constraining for media elements indirectly
holding onto AssociatedURLLoader objects while being stopped
(see associated bug for info.) Consequently, we allow observer removals
while keeping observer set iteration safe & allocation-free -- removals
are recorded while iterating, and removed in one go afterwards.

This is only done for notifyStoppingActiveDOMObjects(), as the other
notifications over context lifecycle observers do not require this
flexibility.

R=
BUG=623755
==========

to

==========
Allow lazy removal of (context) lifecycle observers while stopping.

r402141 imposed the restriction on ContextLifecycleObservers behavior
during stop() notifications of no longer being allowed to remove
observers while handling stop(). That constraint enables iteration
to be handled without allocating a snapshot of the observer set.

That restriction proves too constraining for media elements indirectly
holding onto AssociatedURLLoader objects while being stopped
(see associated bug for info.) Consequently, we allow observer removals
while keeping observer set iteration safe & allocation-free -- removals
are recorded while iterating, and removed in one go afterwards.

This is only done for notifyStoppingActiveDOMObjects(), as the other
notifications over context lifecycle observers do not require this
flexibility.

R=
BUG=623755
==========

[commit-bot: I haz the power, 2016-06-28 12:19:48]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-06-28 12:21:26]

Description was changed from

==========
Allow lazy removal of (context) lifecycle observers while stopping.

r402141 imposed the restriction on ContextLifecycleObservers behavior
during stop() notifications of no longer being allowed to remove
observers while handling stop(). That constraint enables iteration
to be handled without allocating a snapshot of the observer set.

That restriction proves too constraining for media elements indirectly
holding onto AssociatedURLLoader objects while being stopped
(see associated bug for info.) Consequently, we allow observer removals
while keeping observer set iteration safe & allocation-free -- removals
are recorded while iterating, and removed in one go afterwards.

This is only done for notifyStoppingActiveDOMObjects(), as the other
notifications over context lifecycle observers do not require this
flexibility.

R=
BUG=623755
==========

to

==========
Allow lazy removal of (context) lifecycle observers while stopping.

r402141 imposed the restriction on ContextLifecycleObservers behavior
during stop() notifications of no longer being allowed to remove
observers while handling stop(). That constraint enables iteration
to be handled without allocating a snapshot of the observer set.

That restriction proves too constraining for media elements indirectly
holding onto AssociatedURLLoader objects while being stopped
(see associated bug for info.) Consequently, we allow observer removals
while keeping observer set iteration safe & allocation-free -- removals
are recorded while iterating, and removed in one go afterwards.

This is only done for notifyStoppingActiveDOMObjects(), as the other
notifications over context lifecycle observers do not require this
flexibility.

R=
BUG=623755

Committed: https://crrev.com/651bd9f00d9138c0118e9aa923b389d51bb33763
Cr-Commit-Position: refs/heads/master@{#402445}
==========

[commit-bot: I haz the power, 2016-06-28 12:21:27]

Patchset 1 (id:??) landed as
https://crrev.com/651bd9f00d9138c0118e9aa923b389d51bb33763
Cr-Commit-Position: refs/heads/master@{#402445}