DevTools: [JsDocValidator] Be smarter about function name and JSDoc detection

R=aandrey, sergeyv
NOTRY=true

Review URL: https://codereview.chromium.org/319733002

git-svn-id: svn://svn.chromium.org/blink/trunk@175648 bbb929c8-8fbe-4397-9dbb-9b2b20218538