Animate IME adjustment for docked stack through the divider

This makes sure the top stack crop, divider position and bottom stack
surface position moves together with the IME window. Currently the
bottom stack and divider are moving together but top stack crop is
changed immediately.

bug: 27779495
Change-Id: I653ad9093621b218d9c11b0bb2efdddb1d33763e
4 files changed