Added missing depth swizzle backing formats and fixed compressed texture bit calculation. Change-Id: I2390ace1fe5297f9fcad0c873c55dae564a09c43 Reviewed-on: https://chromium-review.googlesource.com/181773 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shannon Woods <shannonwoods@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>