Revert of Simplify LoadableTextTrack::trackElementIndex

Revert of Simplify LoadableTextTrack::trackElementIndex (patchset #1 id:1 of https://codereview.chromium.org/1980013002/ )

Reason for revert:
Seems "WebKit Win Builder (dbg)" didn't approve:

e:\b\build\slave\webkit-win-latest-dbg\build\src\third_party\webkit\source\core\html\track\loadabletexttrack.cpp(70) : warning C4706: assignment within conditional expression

Original issue's description:
> Simplify LoadableTextTrack::trackElementIndex
>
> Count preceding sibling <track> elements in a more straight-forward way.
>
> Also clean-up null-checks of m_trackElement while here (should be non-
> null on construction and then keeps a strong reference.)
>
> Committed: https://crrev.com/0537a6d11bf2ebefcf90fbfec7081e37ef78081a
> Cr-Commit-Position: refs/heads/master@{#393825}

TBR=davve@opera.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/58d9174b50bc167b9ae9212d7ec7f3d0cda625c7
Cr-Commit-Position: refs/heads/master@{#393828}

[fs, 2016-05-16 13:50:35]

Created Revert of Simplify LoadableTextTrack::trackElementIndex

[commit-bot: I haz the power, 2016-05-16 13:50:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1985643003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1985643003/1

[commit-bot: I haz the power, 2016-05-16 13:51:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-05-16 13:52:20]

Description was changed from

==========
Revert of Simplify LoadableTextTrack::trackElementIndex (patchset #1 id:1 of
https://codereview.chromium.org/1980013002/ )

Reason for revert:
Seems "WebKit Win Builder (dbg)" didn't approve:

e:\b\build\slave\webkit-win-latest-dbg\build\src\third_party\webkit\source\core\html\track\loadabletexttrack.cpp(70)
: warning C4706: assignment within conditional expression

Original issue's description:
> Simplify LoadableTextTrack::trackElementIndex
> 
> Count preceding sibling <track> elements in a more straight-forward way.
> 
> Also clean-up null-checks of m_trackElement while here (should be non-
> null on construction and then keeps a strong reference.)
> 
> Committed: https://crrev.com/0537a6d11bf2ebefcf90fbfec7081e37ef78081a
> Cr-Commit-Position: refs/heads/master@{#393825}

TBR=davve@opera.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
==========

to

==========
Revert of Simplify LoadableTextTrack::trackElementIndex (patchset #1 id:1 of
https://codereview.chromium.org/1980013002/ )

Reason for revert:
Seems "WebKit Win Builder (dbg)" didn't approve:

e:\b\build\slave\webkit-win-latest-dbg\build\src\third_party\webkit\source\core\html\track\loadabletexttrack.cpp(70)
: warning C4706: assignment within conditional expression

Original issue's description:
> Simplify LoadableTextTrack::trackElementIndex
>
> Count preceding sibling <track> elements in a more straight-forward way.
>
> Also clean-up null-checks of m_trackElement while here (should be non-
> null on construction and then keeps a strong reference.)
>
> Committed: https://crrev.com/0537a6d11bf2ebefcf90fbfec7081e37ef78081a
> Cr-Commit-Position: refs/heads/master@{#393825}

TBR=davve@opera.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/58d9174b50bc167b9ae9212d7ec7f3d0cda625c7
Cr-Commit-Position: refs/heads/master@{#393828}
==========

[commit-bot: I haz the power, 2016-05-16 13:52:21]

Patchset 1 (id:??) landed as
https://crrev.com/58d9174b50bc167b9ae9212d7ec7f3d0cda625c7
Cr-Commit-Position: refs/heads/master@{#393828}