This was causing more confusion than benefit, so we're removing it.

It's re-defined to empty for now, to avoid touching the ~100 files which
use it, we can remove it completely during a quiet period when it's less
likely to conflict with other work.

Review-Url: https://codereview.chromium.org/2535383005
Cr-Commit-Position: refs/heads/master@{#41393}