Trying to prevent folks from creating large CLs in Options only to
discover we intend to deprecate it shortly. This codifies a few
assumptions we've been making about where new code should go.

BUG=none
R=dbeam@chromium.org
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2719093002
Cr-Commit-Position: refs/heads/master@{#453304}