Remove unused code from MessageCenterNotificationManager.

Remove unused code from MessageCenterNotificationManager.

Bunch of includes are actually unnecessary, simply removed them.

For the fullscreen state, I believe FullscreenNotificationBlocker
can handle it correctly. MessageCenterNotificationManager doesn't
have to handle it anymore.

BUG=None
R=dewittj@chromium.org
TEST=manually

Committed: https://crrev.com/bf6bf16715f0183864ad0b8535ddecc91666ed25
Cr-Commit-Position: refs/heads/master@{#296806}

[dewittj, 2014-09-24 18:15:44]

lgtm!

[Jun Mukai, 2014-09-24 18:18:27]

The CQ bit was checked by mukai@chromium.org

[commit-bot: I haz the power, 2014-09-24 18:19:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/604453002/1

[commit-bot: I haz the power, 2014-09-24 18:50:38]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-09-24 18:50:41]

Try jobs failed on following builders:
  linux_gpu on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/linux_gpu/builds/...)

[Jun Mukai, 2014-09-25 19:51:35]

The CQ bit was checked by mukai@chromium.org

[commit-bot: I haz the power, 2014-09-25 19:53:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/604453002/20001

[commit-bot: I haz the power, 2014-09-25 22:16:18]

Committed patchset #2 (id:20001) as 48f34ededd2af3ca7d08628a54573d7a1a57f186

[commit-bot: I haz the power, 2014-09-25 22:16:52]

Patchset 2 (id:??) landed as
https://crrev.com/bf6bf16715f0183864ad0b8535ddecc91666ed25
Cr-Commit-Position: refs/heads/master@{#296806}