avoid C-only flexible array members

I think we can replace the flexible array member pattern
with this new one using offsetof().  It doesn't seem too error-prone.

Change-Id: Id1c97a4b3ad62aa68a5c485f7692cf71a4868b1d
Reviewed-on: https://skia-review.googlesource.com/139170
Auto-Submit: Mike Klein <mtklein@chromium.org>
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2 files changed