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This adds a vulkan renderer to ozone demo. To use it, build ozone_demo
with enable_vulkan=true set in GN args and run:

  ozone_demo --enable-vulkan

Bug: 581471
Test: ozone_demo --enable-vulkan on X11

Change-Id: Ic773186b1c1634611a28d803273d6dfcdb3aa378
Reviewed-on: https://chromium-review.googlesource.com/1058137
Commit-Queue: Michael Spang <spang@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
Cr-Commit-Position: refs/heads/master@{#560756}