Update MediaKeySession lifetime description to be Oilpan reality-based.

Update MediaKeySession lifetime description to be Oilpan reality-based.

MediaKeys are now referred to by way of WeakMember<> (was: WeakPtr<>);
update comment to reflect that.

Also, remove some redundant WeakPtr.h includes.

R=haraken
BUG=340522
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=191527

[sof, 2015-03-03 13:27:49]

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

[sof, 2015-03-03 13:27:49]

Please take a look.

(Detail noticed while reviewing WeakPtr.h usage in Blink.)

[haraken, 2015-03-03 14:58:27]

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

[haraken, 2015-03-03 14:58:28]

LGTM

Not related to your CL, but MediaKeySession::hasPendingActivity() has code that
depends on MediaKeySession::m_mediaKeys (WeakMember). Is this really correct? It
seems that we're exposing GC behavior to outside...

[sof, 2015-03-03 16:27:31]

On 2015/03/03 14:58:28, haraken wrote:
> LGTM
> 
> Not related to your CL, but MediaKeySession::hasPendingActivity() has code
that
> depends on MediaKeySession::m_mediaKeys (WeakMember). Is this really correct?
It
> seems that we're exposing GC behavior to outside...

Wouldn't that be just fine here?

If there are no JS/script references to MediaKeySession, this session object
will just continue to live until the MediaKeys reference falls away and the next
Oilpan & v8 GCs run. I don't see how that finalization point would be observable
(nor the underlying motivation for extending its lifetime so, it should also be
said :) )

[haraken, 2015-03-04 01:47:41]

On 2015/03/03 16:27:31, sof wrote:
> On 2015/03/03 14:58:28, haraken wrote:
> > LGTM
> > 
> > Not related to your CL, but MediaKeySession::hasPendingActivity() has code
> that
> > depends on MediaKeySession::m_mediaKeys (WeakMember). Is this really
correct?
> It
> > seems that we're exposing GC behavior to outside...
> 
> Wouldn't that be just fine here?
> 
> If there are no JS/script references to MediaKeySession, this session object
> will just continue to live until the MediaKeys reference falls away and the
next
> Oilpan & v8 GCs run. I don't see how that finalization point would be
observable
> (nor the underlying motivation for extending its lifetime so, it should also
be
> said :) )

Ah, makes sense.

[sof, 2015-03-04 14:30:04]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2015-03-04 14:30:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/976613002/20001

[commit-bot: I haz the power, 2015-03-04 15:43:17]

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

[commit-bot: I haz the power, 2015-03-04 15:43:19]

Try jobs failed on following builders:
  mac_blink_rel on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/mac_blink_rel/builds/45940)

[sof, 2015-03-09 07:02:59]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2015-03-09 07:03:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/976613002/20001

[commit-bot: I haz the power, 2015-03-09 08:57:54]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=191527