Clean-up of the system shutdown code paths

Clean-up of the system shutdown code paths

As suggested by +stevenjb in issue 811033002, this CL cleans up the shutdown code paths by
(1) removing the ShutDown method from all system tray delegates
(2) and letting the UI code call directly into ash::Shell

Additionally the ShutdownPolicyObserver is moved to chrome/browser/settings and renamed to ShutdownPolicyHandler

Committed: https://crrev.com/95c6bd1be7480704bb3eb16083bdc3d5f2959173
Cr-Commit-Position: refs/heads/master@{#310477}

[cschuet (SLOW), 2015-01-07 10:14:12]

cschuet@chromium.org changed reviewers:
+ derat@chromium.org, stevenjb@chromium.org, thakis@chromium.org

[cschuet (SLOW), 2015-01-07 10:14:12]

stevenjb@chromium.org: Please review changes in 
ash/system/*
chrome/browser/chromeos/settings/*
chrome/chrome_browser_chromeos.gypi

thakis@chromium.org: Please review changes in 
chrome/browser/ui/webui/*
chrome/chrome_browser_ui.gypi
chrome/chrome_tests_unit.gypi

derat@chromium.org: Please review changes in 
ash/test/*
chrome/browser/ui/ash/*

[stevenjb, 2015-01-07 18:55:12]

lgtm w/alignment fixes

https://codereview.chromium.org/811283003/diff/1/chrome/browser/chromeos/sett...
File chrome/browser/chromeos/settings/shutdown_policy_handler.cc (right):

https://codereview.chromium.org/811283003/diff/1/chrome/browser/chromeos/sett...
chrome/browser/chromeos/settings/shutdown_policy_handler.cc:15: Delegate*
delegate)
align

https://codereview.chromium.org/811283003/diff/1/chrome/browser/chromeos/sett...
File chrome/browser/chromeos/settings/shutdown_policy_handler_unittest.cc
(right):

https://codereview.chromium.org/811283003/diff/1/chrome/browser/chromeos/sett...
chrome/browser/chromeos/settings/shutdown_policy_handler_unittest.cc:24: public
ShutdownPolicyHandler::Delegate {
align

[Nico, 2015-01-07 18:58:07]

My files lgtm. (consider running `git cl format` to get the alignment fixes that
stevenjb asked for)

[Daniel Erat, 2015-01-07 20:16:27]

lgtm

[cschuet (SLOW), 2015-01-08 08:06:28]

The CQ bit was checked by cschuet@chromium.org

[commit-bot: I haz the power, 2015-01-08 08:07:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/811283003/40001

[commit-bot: I haz the power, 2015-01-08 10:08:57]

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

[commit-bot: I haz the power, 2015-01-08 10:08:58]

Exceeded time limit waiting for builds to trigger.

[cschuet (SLOW), 2015-01-08 10:38:19]

The CQ bit was checked by cschuet@chromium.org

[commit-bot: I haz the power, 2015-01-08 10:39:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/811283003/40001

[commit-bot: I haz the power, 2015-01-08 11:33:10]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-01-08 11:33:55]

Patchset 3 (id:??) landed as
https://crrev.com/95c6bd1be7480704bb3eb16083bdc3d5f2959173
Cr-Commit-Position: refs/heads/master@{#310477}