LatinIME: Set navigation bar color to KB background

Black navbar is especially irritating in light mode. We have to use
the deprecated API because with the new one the close and IME switcher
icons in the navbar don't get drawn in the correct colors.

Includes Id0e624c590166dd4537c5bec218b8acd4842fa64.

Change-Id: Ibf81a90a238583084a102af8b70a16f5b894e5a2