Clarify XSAN instructions

No-Try: true
Docs-Preview: https://skia.org/?cl=103680
Bug: skia:
Change-Id: I941708d7a3eb1e5a2d11d129cfbef0cec5bd1256
Reviewed-on: https://skia-review.googlesource.com/103680
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
1 file changed