Don't use ErrorOrResult in VertexBuffer.h. This enables the error refactor for D3D. Bug: angleproject:2752 Change-Id: I7bb293d6c271d0bffb4d00b55029426b6cd0a42e Reviewed-on: https://chromium-review.googlesource.com/1167208 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>