[win] Add signin support for the app launcher.

[win] Add signin support for the app launcher.

This relands r178795, with the navigation to the sign in screen deferred until
the app list is shown and sign in is needed.

TBR=sky@chromium.org, atwilson@chromium.org, rogerta@chromium.org, xiyuan@chromium.org
BUG=159733
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=179302

[benwells, 2013-01-29 02:41:27]

Hey koz, patch set 1 already has / had lgtms from all owners needed. Could you
look at the changes in patch set 2, that is all that has changed in this patch.

[koz (OOO until 15th September), 2013-01-29 02:53:11]

lgtm

[commit-bot: I haz the power, 2013-01-29 03:50:58]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/benwells@chromium.org/12095027/2001

[commit-bot: I haz the power, 2013-01-29 04:14:57]

Sorry for I got bad news for ya.
Compile failed with a clobber build on mac.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac&number...
Your code is likely broken or HEAD is junk. Please ensure your
code is not broken then alert the build sheriffs.
Look at the try server FAQ for more details.

[commit-bot: I haz the power, 2013-01-29 06:16:00]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/benwells@chromium.org/12095027/11002

[commit-bot: I haz the power, 2013-01-29 06:39:25]

Sorry for I got bad news for ya.
Compile failed with a clobber build on mac.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac&number...
Your code is likely broken or HEAD is junk. Please ensure your
code is not broken then alert the build sheriffs.
Look at the try server FAQ for more details.