https://bugs.webkit.org/show_bug.cgi?id=103420

Reviewed by Eric Carlson.

There were some assumptions that <track> elements are valid only
if the parent <media> is in document. This change relaxes this
assumption so that <track> is valid when it has <media> as a
parent regardless whether the <media> is in the document or not.

HTMLMediaElement::didAddTrack and didRemoveTrack are now called
when the <track> is inserted to or removed from the parent <media>
element.

Test: media/track/track-node-add-remove.html

* html/HTMLMediaElement.cpp:
(WebCore::HTMLMediaElement::didRemoveTrack):
Renamed from willRemoveTrack() to reflect the timing. This was once called from
Node::willRemove(), which was removed a while ago.
* html/HTMLMediaElement.h:
(HTMLMediaElement):
* html/HTMLTrackElement.cpp:
(WebCore::HTMLTrackElement::insertedInto):
The old code notified parent <media> only if the subtree became a part of the document.
Now it notifies the <media> when this <track> becomes a child of that <media>.

(WebCore::HTMLTrackElement::removedFrom):
The old code notifies the parent <media> every time as long as the parent is available.
Now it notifies the <media> only if this <track> is removed from the parent <media>.
This matches how corresponding notification is done in insertedInto().

* html/track/LoadableTextTrack.cpp:
(WebCore::LoadableTextTrack::trackElementIndex):

LayoutTests: HTMLMediaElement's .textTracks property does not reflect <track> element
https://bugs.webkit.org/show_bug.cgi?id=103420

Reviewed by Eric Carlson.

* media/track/track-node-add-remove-expected.txt: Added.
* media/track/track-node-add-remove.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@136131 268f45cc-cd09-0410-ab3c-d52691b4dbfc