Navigation bar dimensions (1/2)

Based off this commit from @cristianomatos, https://github.com/cristianomatos/android_frameworks_base/commit/68270b63c58c3fd7ea1ba283c97ed37b5fec87a7
- Modified to work with our current nav bar setup.

Change-Id: I02002ea332d78d5e8181b377c7e0d9f57078c6c1
Signed-off-by: Lokesh Chamane <lokesh.c703@gmail.com>