Prevent triggering orientation changes until previous completes.

Currently we defer rotation while the screen rotation animation
is animating, but there is an additional interval after the animation
completes where the display may not yet be unfrozen and attempting to
rotate again will not work.

Bug: 31749456
Change-Id: I5f6830d85fb326d5032b597cbed1b767f0b627f5
1 file changed