Change recents UIs to do task switches.

When switching to a recent task that is currently active, do a
task switch instead of a start activity, so the activity is brought
back in its exact same state.

Also fix problem in phone recents where the icon would disappear
after you touch it.

Change-Id: Id5c8478f8c33c90f52fbb4d969037d2bf5af9fff
3 files changed