Disallow adding ContextLifecycleObservers during iteration.

Disallow adding ContextLifecycleObservers during iteration.

The implementation of ContextLifecycleNotifier disallows the addition
of ActiveDOMObjects while delivering its notifications, by way of
a RELEASE_ASSERT(). This prevents ending up in inconsistent states where
(e.g.) instructing the ActiveDOMObjects to stop would lead to the
creation of new, but running, ActiveDOMObjects.

Extend this restriction to encompass all ContextLifecycleObservers; none
may be added while iterating over the registered ActiveDOMObjects. This
allows us to simplify the underlying implementation somewhat.

R=haraken
BUG=462949
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=192377

[sof, 2015-03-23 14:23:33]

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

[sof, 2015-03-23 14:23:33]

please take a look.

Had another look at the need for ContextLifecycleNotifier::addObserver(), and I
think we can avoid it, without downsides. Trybots bear that out - wdyt?

[haraken, 2015-03-23 14:30:43]

LGTM

https://codereview.chromium.org/1024543004/diff/1/Source/platform/LifecycleNo...
File Source/platform/LifecycleNotifier.h (right):

https://codereview.chromium.org/1024543004/diff/1/Source/platform/LifecycleNo...
Source/platform/LifecycleNotifier.h:72: IterationType m_iterating;

We can probably change this to bool (in a follow-up).

https://codereview.chromium.org/1024543004/diff/1/Source/platform/LifecycleOb...
File Source/platform/LifecycleObserver.h (right):

https://codereview.chromium.org/1024543004/diff/1/Source/platform/LifecycleOb...
Source/platform/LifecycleObserver.h:40: LifecycleObserver(Context* context)

Add explicit.

[sof, 2015-03-23 15:06:29]

https://codereview.chromium.org/1024543004/diff/1/Source/platform/LifecycleOb...
File Source/platform/LifecycleObserver.h (right):

https://codereview.chromium.org/1024543004/diff/1/Source/platform/LifecycleOb...
Source/platform/LifecycleObserver.h:40: LifecycleObserver(Context* context)
On 2015/03/23 14:30:43, haraken wrote:
> 
> Add explicit.

Done, along with making the ctor protected.

[sof, 2015-03-23 16:39:17]

The CQ bit was checked by sigbjornf@opera.com

[sof, 2015-03-23 16:39:18]

The patchset sent to the CQ was uploaded after l-g-t-m from haraken@chromium.org
Link to the patchset: https://codereview.chromium.org/1024543004/#ps20001
(title: "tidier LifecycleObserver ctor")

[commit-bot: I haz the power, 2015-03-23 16:39:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1024543004/20001

[commit-bot: I haz the power, 2015-03-23 18:11:21]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=192377