Remove SigninDelegateObserver.

Remove SigninDelegateObserver.

Now that the AppListViewDelegate receives signin notifications, the
SigninDelegateObserver is unnecessary. This will also fix a DCHECK
that was being failing due to ChromeSigninDelegate's implementation
of listening to signin events.

Specifically, the DCHECK would happen after signing in from the app
launcher, signing out, and then signing in again from somewhere else
(e.g chrome:settings). ChromeSigninDelegate uses a SigninTracker
which expects the signin to be in a particular state. On the second
signin the SigninTracker hasn't been reset and does not like the
state it's in.

An alternative fix to this DCHECK is to delete the SigninTracker on
signin success/failure but since this code is now unnecessary,
we may as well remove it.

BUG=271933
TEST=No functional changes

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=218991

[tapted, 2013-08-22 04:26:54]

Cool - lgtm. But, if this fixes a crash, you should definitely have a TEST= line
.

I think I was planning to make the app list pop up again on a successful signin
for the case where a user clicks the signin button on the app list, but better
to rip out the code while it's dead.

[koz (OOO until 15th September), 2013-08-22 04:38:43]

lgtm

It's not obvious from the bug or this change what the crash was caused by, if
it's not too complicated could you add an explanation in the description?

[commit-bot: I haz the power, 2013-08-22 07:01:00]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/calamity@chromium.org/22825025/1

[commit-bot: I haz the power, 2013-08-22 07:49:59]

Retried try job too often on win_x64_rel for step(s) compile
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_x64_re...

[commit-bot: I haz the power, 2013-08-22 08:10:18]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/calamity@chromium.org/22825025/28001

[commit-bot: I haz the power, 2013-08-22 10:52:57]

Change committed as 218991