parser and the preparser, so that they contain the same set of methods,
with the same signatures.  It mainly flags some traits methods as const.
It also contains a small cosmetic change in the definition of CHECK_OK.

R=adamk@chromium.org, marja@chromium.org
BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2258123002
Cr-Commit-Position: refs/heads/master@{#38767}