Oilpan: Change LoadableTextTrack::m_trackElement a strong Member

Oilpan: Change LoadableTextTrack::m_trackElement a strong Member

This CL changes LoadableTextTrack::m_trackElement from a WeakMember to a Member.

In non-oilpan, LoadableTextTrack::m_trackElement is implemented as a weak pointer,
but it's just because there is no way in non-oilpan to make it a strong pointer
without creating a cycle. Ideally LoadableTextTrack::m_trackElement should be
implemented as a strong pointer. This is possible in oilpan, and this CL makes the change.

BUG=340522
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177052

[haraken, 2014-06-24 09:22:35]

philipj@, glenn@: Would you take a look at this?

I think LoadableTextTrack::m_trackElement should be a strong pointer in terms of
semantics, but I'm not 100% sure :)

[sof, 2014-06-25 21:15:47]

lgtm - LoadableTextTrack should be reachable from HTMLTrackElement for as long
as the latter lives. I don't think you can put an upper bound on the lifetime of
the connection in the other direction either, so keeping a strong Member in both
places seems correct.

The reason why we left it a WeakMember initially is explained in
https://codereview.chromium.org/244493002/#msg22

[haraken, 2014-06-26 00:40:34]

philipj, glenn: Would you take a look at this one-line CL?

[philipj_slow, 2014-06-26 08:55:23]

LGTM.

If you like, there's some null-checking on m_trackElement that can now be made
conditional on ENABLE(OILPAN), I think.

It would be nice if the commit message were wrapped at 70-80 columns.

[haraken, 2014-06-26 13:02:44]

Thanks for review!

> If you like, there's some null-checking on m_trackElement that can now be made
> conditional on ENABLE(OILPAN), I think.
> 
> It would be nice if the commit message were wrapped at 70-80 columns.

Done.

[haraken, 2014-06-26 13:03:03]

The CQ bit was checked by haraken@chromium.org

[commit-bot: I haz the power, 2014-06-26 13:04:53]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/haraken@chromium.org/351563005/20001

[commit-bot: I haz the power, 2014-06-27 03:19:00]

Change committed as 177052