Remove TextTrackCue::notifyRegionWhenRemovingDisplayTree

Remove TextTrackCue::notifyRegionWhenRemovingDisplayTree

This method is only called in CueTimeline::removeCue, and in there it's
only used to reset the m_notifyRegion flag in VTTCue temporarily while
calling removeDisplayTree. Remove notifyRegionWhenRemovingDisplayTree
in favor of passing a flag to removeDisplayTree.
In order to achieve this though we need to hoist the submerged call
to removeDisplayTree from TextTrackCue::setIsActive. This in turn makes
it clear that removeDisplayTree was called twice in the relevant
context.

BUG=321654, 322434
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=190547

[fs, 2015-02-19 17:27:56]

fs@opera.com changed reviewers:
+ philipj@opera.com

[philipj_slow, 2015-02-20 10:41:16]

The CQ bit was checked by philipj@opera.com

[philipj_slow, 2015-02-20 10:41:17]

lgtm

Less member state yay

[commit-bot: I haz the power, 2015-02-20 10:44:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/939193002/20001

[commit-bot: I haz the power, 2015-02-20 10:47:34]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=190547