Remove obsolete DEBUG and NDEBUG macro dance.

Remove obsolete DEBUG and NDEBUG macro dance.

The original intention of this seemed to have been to enable DEBUG when
NDEBUG was not defined within Google3. Everything since then was just
added to avoid the "#error" below checking for consistency from firing.
Semantics have also shifted along the way. I vote for dropping this.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/1315063007

Cr-Commit-Position: refs/heads/master@{#30591}