Check that ime visibility changes in stack view

This fixes a minor animation issue when expanding the stack while
the IME is visible.

Flag: EXEMPT bug fix
Bug: 379474417
Test: manual
       - have a floating bubble
       - launch app
       - request IME in the app
       - tap on bubble to expand
       - observe expand animation is smooth
Change-Id: I2fd4031004f482af94162ffa0188b527ba874813