DevTools: Fix JSDoc and code landed in r169951.

R=pfeldman
BUG=337138
NOTRY=true

Review URL: https://codereview.chromium.org/212503002

git-svn-id: svn://svn.chromium.org/blink/trunk@170034 bbb929c8-8fbe-4397-9dbb-9b2b20218538