DevTools: [CodeMirror] roll codemirror comment plugin

The patch pulls upstream changes in comment addon that fix CSS
commenting bug.

BUG=402411
R=vsevik

Review URL: https://codereview.chromium.org/495353002

git-svn-id: svn://svn.chromium.org/blink/trunk@180794 bbb929c8-8fbe-4397-9dbb-9b2b20218538