This method is useful for the Vulkan back-end as well as D3D11. It can
produce a uniform block layout for the default uniform blocks as well
as for interface blocks. Put it in blocklayout.h in the translator.

BUG=angleproject:2167

Change-Id: I13160906921da439746c1811a623006250aaeefd
Reviewed-on: https://chromium-review.googlesource.com/713941Reviewed-by: Frank Henigman <fjhenigman@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>