Replace HTMLMediaElement::isActive() with Node::inActiveDocument()

Replace HTMLMediaElement::isActive() with Node::inActiveDocument()

The m_active flag was previously named m_inActiveDocument:
https://codereview.chromium.org/26270004

Because m_active is updated in HTMLMediaElement::insertedInto(),
removedFrom() and stop(), HTMLMediaElement::isActive() it is very
similar to Node::inActiveDocument(), with the difference that in the
early stages of a Document's life, inActiveDocument() is false while
isActive() is true.

In RenderVideo, the difference is irrelevant, because nothing is being
rendered at that point in the lifecycle.

The usage in HTMLMediaElement::endIgnoringTrackDisplayUpdateRequests()
was added to fix failing tests in
https://bugs.webkit.org/show_bug.cgi?id=105606:

media/track/tracklist-is-reachable.html
media/track/text-track-cue-is-reachable.html
media/track/text-track-is-reachable.html
media/track/track-webvtt-tc005-header-comment.html
media/track/track-webvtt-tc004-magic-header.html
media/track/track-webvtt-tc016-align-positioning.html

All of these are still passing.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185854

[philipj_slow, 2014-11-21 11:51:39]

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

[philipj_slow, 2014-11-21 11:51:40]

PTAL

[fs, 2014-11-21 12:17:27]

lgtm

[philipj_slow, 2014-11-21 22:44:17]

The CQ bit was checked by philipj@opera.com

[commit-bot: I haz the power, 2014-11-21 22:44:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/594533002/20001

[commit-bot: I haz the power, 2014-11-21 22:51:06]

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

[commit-bot: I haz the power, 2014-11-21 22:51:07]

Try jobs failed on following builders:
  blink_presubmit on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/blink_presubmit/builds/2...)

[philipj_slow, 2014-11-23 19:58:41]

rebase

[philipj_slow, 2014-11-23 19:58:49]

The CQ bit was checked by philipj@opera.com

[commit-bot: I haz the power, 2014-11-23 19:59:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/594533002/40001

[commit-bot: I haz the power, 2014-11-23 21:09:09]

Committed patchset #3 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=185854