Misc fixes for IME adjust

- Use thinner divider when IME adjusted

- Dim non-focused stack

- Restrict IME adjustment so that top pane is shrunk to 30% at most

- Move top stack up together with IME adjust

- Move bottom stack up even when not focused for thinner divider

bug: 28175599

Change-Id: I83556535e5a171f0ec28d88429186fa1315b910c