Merge 6103e22c from honeycomb-mr1. do not merge.

LayoutLib: custom styles override the default style instead of replacing it.

Intead of reading either the custom or the default style for a widget, we
read both and use the values from the custom style if it exists, or
from the default style otherwise.

Change-Id: Ibcec2e9b1e8a95295ab26ede145c287ff2f30be4