Add offset to uniform blocks in Vulkan

This is the first step to being able to use push constants.

BUG=skia:5039

Change-Id: I49edea8faacf78814036ce3b3f9f2814974cf2c7
Reviewed-on: https://skia-review.googlesource.com/7448
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
2 files changed