Use base::size rather than arraysize in extensions/.

This is purely a mechanical change; there is no intended behavior change.

BUG=837308
TBR=rdevlin.cronin@chromium.org

Change-Id: I1893e0d4c9fc96075be5803d4acb3e938a757367
Reviewed-on: https://chromium-review.googlesource.com/c/1390729
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#618877}
66 files changed