Fixes divider position after minimizing and unminimizing with ime open

Minimizing with the ime would cause visual glitches with the divider and
unminiming after would set the wrong position leaving graphical errors.
Record the position before minimizing when adjusting for ime and do not
set that position when the ime is still adjusted. Also added animation
for the divider when adjusting for ime.

Bug: 36603383
Test: manual
Change-Id: I456f3a726c62d130dce6c58c2245982e7f46454c