Replace placeholder extension ID for hotwording shared module with ID of module uploaded to the Chr…

Replace placeholder extension ID for hotwording shared module with ID of module uploaded to the Chrome web store.

Also, auto-install hotword shared module when hotwording is enabled.

BUG=397019
Committed: https://crrev.com/075d1694c7f5594a923bb6275cbbd21f0cfa2441
Cr-Commit-Position: refs/heads/master@{#296890}

[Anand Mistry (off Chromium), 2014-09-25 02:57:03]

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

[James Hawkins, 2014-09-25 18:02:10]

lgtm

[rpetterson, 2014-09-26 03:53:13]

lgtm

[Anand Mistry (off Chromium), 2014-09-26 03:57:39]

The CQ bit was checked by amistry@chromium.org

[commit-bot: I haz the power, 2014-09-26 03:58:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/599053004/20001

[commit-bot: I haz the power, 2014-09-26 05:33:41]

Committed patchset #2 (id:20001) as 8c3dc46b04706b2858bea0bf8fc198d97b303bbc

[commit-bot: I haz the power, 2014-09-26 05:34:16]

Patchset 2 (id:??) landed as
https://crrev.com/075d1694c7f5594a923bb6275cbbd21f0cfa2441
Cr-Commit-Position: refs/heads/master@{#296890}