chromeos: Remove UpdateObserver, which has been unused for long.

chromeos: Remove UpdateObserver, which has been unused for long.

We don't show a notification panel when an update is ready.
Asked kanliu@ and he was okay with removing this.

TEST=chrome and tests build.
BUG=chromium-os:16564
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=106871

[oshima, 2011-10-21 22:53:55]

LGTM

[commit-bot: I haz the power, 2011-10-22 06:06:30]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/satorux@chromium.org/8369009/1

[commit-bot: I haz the power, 2011-10-22 08:54:41]

The commit queue went berserk retrying too often for a
seemingly flaky test. Builder is win_rel, revision is 106848, job name
was 8369009-1 (retry) (retry) (retry) (retry).

[commit-bot: I haz the power, 2011-10-22 17:02:51]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/satorux@chromium.org/8369009/1

[commit-bot: I haz the power, 2011-10-22 19:45:09]

The commit queue went berserk retrying too often for a
seemingly flaky test. Builder is win_rel, revision is 106859, job name
was 8369009-1 (retry) (retry) (retry) (retry).