DevTools: [CodeMirror] add forgotten images

This is a follow-up to the r179654 which adds forgotten images to
the resource bundle.

BUG=397217
TBR=vsevik
NOTRY=true

Review URL: https://codereview.chromium.org/457623002

git-svn-id: svn://svn.chromium.org/blink/trunk@179808 bbb929c8-8fbe-4397-9dbb-9b2b20218538