Fix extra offset of the split layout

Use parent based coordinate instead of screen based coordinate when
indicating split surfaces' position so they won't be offset unexpectedly
when its parent is not at (0, 0).

Fix: 210696145
Test: check split UI when enabled "render apps below cutout area"
Change-Id: I65399f5ef2975e7ef376d161c41de2cfb7ed29dc
3 files changed