Revert "Revert "Remove IME surface when occured in multi-window mode""

This reverts commit 2a38a356.

Reason for revert: The original CL was reverted for b/158836294 and it turned out to be innocent. Re-land the CL.

Bug: b/155660756

Change-Id: Iada83e80059e7cb9566bb7ad4e4c9909b4ed794a