Store and check IME window vis value before update

This stores the last reported value of IME window vis (similar to the
IME back disposition), to be checked against the new value in avoiding
duplicate updates.

Flag: EXEMPT refactor
Bug: 364270925
Test: presubmit
Change-Id: I72e81f259b33eecfc956c78fa0da3209b492d99c
1 file changed