Avoid loading the chime when the hotword background page is opened.

Avoid loading the chime when the hotword background page is opened.

Loading the chime causes the page to create an audio output stream.
Setting preload=none on the audio tag prevents the chime from being
loaded on startup, and instead causes it to be loaded on demand when the
chime is played.

BUG=432699, 397019
Committed: https://crrev.com/8b216d8eac67c5e5f8de4414e297a214c727b77d
Cr-Commit-Position: refs/heads/master@{#304975}

[Anand Mistry (off Chromium), 2014-11-19 23:16:13]

amistry@chromium.org changed reviewers:
+ rlp@chromium.org

[Anand Mistry (off Chromium), 2014-11-19 23:16:14]

Dale: FYI.

[rpetterson, 2014-11-20 01:18:16]

lgtm

[Anand Mistry (off Chromium), 2014-11-20 02:15:17]

The CQ bit was checked by amistry@chromium.org

[commit-bot: I haz the power, 2014-11-20 02:16:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/741873002/1

[commit-bot: I haz the power, 2014-11-20 04:41:58]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-20 04:42:38]

Patchset 1 (id:??) landed as
https://crrev.com/8b216d8eac67c5e5f8de4414e297a214c727b77d
Cr-Commit-Position: refs/heads/master@{#304975}