DevTools: [CodeMirror] roll comment plugin

This patch rolls comment plugin from the upstream to the
revision @e59601 which fixes string corruption bug.
Upstream bug: https://github.com/marijnh/CodeMirror/issues/1975

BUG=321748
TBR=vsevik

Review URL: https://codereview.chromium.org/110433002

git-svn-id: svn://svn.chromium.org/blink/trunk@163440 bbb929c8-8fbe-4397-9dbb-9b2b20218538