Don't notify existing observers in SupervisedUserWhitelistService::AddSiteListsChangedCallback().

Don't notify existing observers in SupervisedUserWhitelistService::AddSiteListsChangedCallback().

The additional callbacks caused the SupervisedUserUrlFilter to update its filter unnecessarily, which in turn flakily quit the observer run loop too early.

This CL fixes the flakiness by using the main thread message loop for the SupervisedUserUrlFilter (removing non-determinism), spreading out the synchronization points for site list updates and URL filter updates, and adding additional sanity checks about observed changes.

BUG=452071
Committed: https://crrev.com/1ec543761663537283abbe2f2ddef51b6320f995
Cr-Commit-Position: refs/heads/master@{#313483}

[Bernhard Bauer, 2015-01-27 17:30:34]

bauerb@chromium.org changed reviewers:
+ treib@chromium.org

[Bernhard Bauer, 2015-01-27 17:30:35]

Please review!

[Marc Treib, 2015-01-28 09:01:15]

LGTM!

https://codereview.chromium.org/875423002/diff/40001/chrome/browser/supervise...
File chrome/browser/supervised_user/supervised_user_service_unittest.cc (right):

https://codereview.chromium.org/875423002/diff/40001/chrome/browser/supervise...
chrome/browser/supervised_user/supervised_user_service_unittest.cc:61: //
|quit_called_| will be initialied in Reset().
typo: initialiZed

[Bernhard Bauer, 2015-01-28 10:49:58]

https://codereview.chromium.org/875423002/diff/40001/chrome/browser/supervise...
File chrome/browser/supervised_user/supervised_user_service_unittest.cc (right):

https://codereview.chromium.org/875423002/diff/40001/chrome/browser/supervise...
chrome/browser/supervised_user/supervised_user_service_unittest.cc:61: //
|quit_called_| will be initialied in Reset().
On 2015/01/28 09:01:14, Marc Treib wrote:
> typo: initialiZed

Done.

[Bernhard Bauer, 2015-01-28 10:57:48]

The CQ bit was checked by bauerb@chromium.org

[commit-bot: I haz the power, 2015-01-28 10:58:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/875423002/60001

[commit-bot: I haz the power, 2015-01-28 11:58:09]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-01-28 12:01:04]

Patchset 4 (id:??) landed as
https://crrev.com/1ec543761663537283abbe2f2ddef51b6320f995
Cr-Commit-Position: refs/heads/master@{#313483}