Add guards around dxgi_support_table.h. BUG=angleproject:2082 Change-Id: I6f20502bac3c664d5ef8c6d65b244c37a5727f26 Reviewed-on: https://chromium-review.googlesource.com/545458 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>