AudioPlayer: Fix the way to find a track element with given index.

AudioPlayer: Fix the way to find a track element with given index.

Current audio player uses shady dom, so '::shadow' in the selecter is invalid.
Polymer's standard way to locate local dom should be used.

BUG=554451
TEST=manually

Committed: https://crrev.com/c66b6928de9b6bb20669ceecf8673480bea0ddc2
Cr-Commit-Position: refs/heads/master@{#363717}

[fukino, 2015-12-07 11:34:26]

fukino@chromium.org changed reviewers:
+ yawano@chromium.org

[fukino, 2015-12-07 11:34:27]

PTAL. Thanks!

[yawano, 2015-12-07 12:23:15]

lgtm. Thank you!

[fukino, 2015-12-08 02:20:05]

On 2015/12/07 12:23:15, yawano wrote:
> lgtm. Thank you!

Thank you!

[fukino, 2015-12-08 02:20:08]

The CQ bit was checked by fukino@chromium.org

[commit-bot: I haz the power, 2015-12-08 02:20:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1510453002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1510453002/1

[commit-bot: I haz the power, 2015-12-08 02:46:36]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-12-08 02:47:56]

Description was changed from

==========
AudioPlayer: Fix the way to find a track element with given index.

Current audio player uses shady dom, so '::shadow' in the selecter is invalid.
Polymer's standard way to locate local dom should be used.

BUG=554451
TEST=manually
==========

to

==========
AudioPlayer: Fix the way to find a track element with given index.

Current audio player uses shady dom, so '::shadow' in the selecter is invalid.
Polymer's standard way to locate local dom should be used.

BUG=554451
TEST=manually

Committed: https://crrev.com/c66b6928de9b6bb20669ceecf8673480bea0ddc2
Cr-Commit-Position: refs/heads/master@{#363717}
==========

[commit-bot: I haz the power, 2015-12-08 02:47:57]

Patchset 1 (id:??) landed as
https://crrev.com/c66b6928de9b6bb20669ceecf8673480bea0ddc2
Cr-Commit-Position: refs/heads/master@{#363717}