[javascript mode] Don't get confused by trailing commas in parentheses
[javascript mode] Don't get confused by trailing commas in parentheses

Closes #6120

nightwing/CodeMirror,wingify/CodeMirror,nightwing/CodeMirror,pabloferz/CodeMirror,dperetti/CodeMirror,dperetti/CodeMirror,codio/CodeMirror,pabloferz/CodeMirror,codio/CodeMirror,hackmdio/CodeMirror,nightwing/CodeMirror,hackmdio/CodeMirror,codio/CodeMirror,dperetti/CodeMirror,wingify/CodeMirror,wingify/CodeMirror,hackmdio/CodeMirror,pabloferz/CodeMirror