DevTools: [CodeMirror] roll comment plugin to @7dfbf42

BUG=414302
R=vsevik

Review URL: https://codereview.chromium.org/658563005

git-svn-id: svn://svn.chromium.org/blink/trunk@183998 bbb929c8-8fbe-4397-9dbb-9b2b20218538