Remove Extension Loaded/Unloaded notifications from LocationBarView(Mac)

Remove Extension Loaded/Unloaded notifications from LocationBarView(Mac)

Having the views observe these notifications is strange -- they don't know when
page actions are updated in any other ways, so they shouldn't need to know for
this. Move the notifications to LocationBarController.

Bonuses:
- Less code! By 50 lines!
- Remove four deprecated notification uses!

This has a very loose dependency on https://codereview.chromium.org/508563003/.

BUG=407672
Committed: https://crrev.com/5681e2f220f4bab29a5bd504dec15631eb8c1b4c
Cr-Commit-Position: refs/heads/master@{#292225}

[Devlin, 2014-08-26 23:37:21]

rdevlin.cronin@chromium.org changed reviewers:
+ avi@chromium.org, finnur@chromium.org, pkasting@chromium.org

[Devlin, 2014-08-26 23:37:21]

Finnur, Avi, and Peter, please take a look when you can.
finnur: everything
avi: c/b/ui/cocoa/
pkasting: c/b/ui/views/

Cheers!

[Avi (use Gerrit), 2014-08-26 23:43:45]

Cocoa lgtm

[Peter Kasting, 2014-08-26 23:57:07]

LGTM

[Finnur, 2014-08-27 11:35:36]

Moar moderniceing of koad! Woot! Woot!

LGTM

[Devlin, 2014-08-27 20:03:37]

The CQ bit was checked by rdevlin.cronin@chromium.org

[commit-bot: I haz the power, 2014-08-27 20:04:29]

CQ is trying da patch. Follow status at

https://chromium-status.appspot.com/cq/rdevlin.cronin@chromium.org/505373002/...

[commit-bot: I haz the power, 2014-08-27 21:22:02]

Committed patchset #2 (id:20001) as 76c028bfb10ef771094a194378161ed1fb93439c

[commit-bot: I haz the power, 2014-09-10 02:54:06]

Patchset 2 (id:??) landed as
https://crrev.com/5681e2f220f4bab29a5bd504dec15631eb8c1b4c
Cr-Commit-Position: refs/heads/master@{#292225}