Prevent rendering divider bar into wrong orientation

The display area's bounds and orientation changed might be callbacked
seperatedly when the device's folded state changed, causing the
SplitLayout rendered divider bar into wrong orientation. This makes sure
to update divider bar and split layout correspondingly when the
orientation, rotation and root bounds chagned.

Fix: 189101216
Test: atest WMShellUnitTests
Change-Id: Ie5d7132e4122b82d9b5b404a40f97cca3095ce2c