DevTools: Hiding some new types before publishing a new protocol.json version.

BUG=None
R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/23478026

git-svn-id: svn://svn.chromium.org/blink/trunk@157603 bbb929c8-8fbe-4397-9dbb-9b2b20218538