Properly size KG camera animation for translucent bars.

The KGHV now plumbs insets information down into the camera
so that it can leave space for the navigation bar if the KG
window happens to extend underneath it. The camera widget
preview must therefore be rendered to fit the size of the
smaller inset content area, which means there's now a hole
at the bottom; we fill this bottom area during animation
with a fake navigation bar: a black view occupying the area
underneath the real navbar.

Bug: 11048015
Change-Id: Ia23b62e155686ad9f17a25ccc14f6c97b53dafea