Revert "Do not use last app rotation as default."

This reverts commit 4bd149ef

This change introduced a regression in the device rotation policy.  Suppose you hold the device in landscape orientation then put it flat on a table.  At this time, the accelerometer has no information about which way the device is oriented so the sensor expresses no preference over the orientation.  Now switch to an application that forces portrait.  Then go back to the original app that auto-rotates.  We should remain portrait from this point onwards unless the device is picked up and we have accelerometer information from which to establish a new preferred orientation.

Bug: 7173556
Change-Id: I3684af3369e4ea55042081e19d96773c4d4bbe76