ActionBar: Compute required items prior to optional items

When computing if a item should be shown in the action bar, required items need to be compute prior
to optional ones. Otherwise, in some cases (when the optional menu goes to the left of required
items then the algorithm could determine that optional has space to be shown and force the show of
required items, causing the required items to not be shown).
A concrete case is in the Email app. In the message_view_fragment_option.xml are defined 5 menus,
that when are all shown (xe: in Exchange mailbox account type) the bar is complete filled. But if
the overflow button is forced to be shown (the device has no permanent menu key) the overflow button
overlaps the older button, because space of 'ifRoom' items are wrong computed.

Change-Id: I6fc8e3e202d76f9704d7ec2383c7ee6f7b05ba76
Set foreground priority for shutdown receivers.

The broadcast of ACTION_SHUTDOWN has a timeout of 10 seconds. To
reduce the risk of hitting the timeout and speeding up the
shutdown sequence in ShutdownThread we set the priority of the
BroadcastReceivers to FLAG_RECEIVER_FOREGROUND.

We have seen that this change reduces the shutdown time when
the system is under heavy load.

Change-Id: I22cbf6af8cf6fc4bdefaa1c3da8a7eed7e7b7674