Fix issue #16794553: Duplicate ArrayMap entries in Bundle...

...can lead to launching of un-exported activities

We now validate the array map after unparcelling to make sure there
are no duplicate keys.

And to make up for the performance overhead this introduces, I switched
the parcelling/unparcelling code to write keys as explicit string
objects rather than generic values.  There was no reason to use generic
values since the write method itself only accepts an array map with
String keys.

Change-Id: I57bda9eb79ceaaa9c1b94ad49d9e462b52102149
Do not persist and restore the media button event receiver

Do not persist the media button event receiver.
Do not restore the media button event receiver on behalf of the
  application that registered. Prevents reported vulnerability.

Bug 15428797

Change-Id: I7ca3e7fccb165c55b23f471c00e0ed77436f7dc1