Fix issue #5229575: Youtube link shared through messaging is not...

...opening after selecting option "Youtube" as a luncher.

Also:

* Tweak window animations so that the wallpaper exist animations do not
stop too early (causing the wallpaper to suddenly disappear).
* Make sure no input is being processed while booting, to avoid
accidentally doing things especially in the upgrade dialog.
* Some other small cleanup.

Change-Id: I40a6b53731991d4e31ac4502e3d85f0e47507481