Fix split dim when IME shown

ImePositionProcessor didn't handle dim if it didn't not offset
layout, but when landscape, the layout will not offset. It cause
dim value didn't apply.

Fix this by checking both offset and dim value.

Fix: 200757897
Test: manual
Test: pass existing tests
Change-Id: I709b69c8e2d102d0e8237998b26f45c70805bf23