highlighter: reuse created token id chunks for performance
highlighter: reuse created token id chunks for performance

It may be better that we remove all existing records on many keywords
case.

kenhys/groonga,komainu8/groonga,groonga/groonga,groonga/groonga,groonga/groonga,naoa/groonga,komainu8/groonga,komainu8/groonga,naoa/groonga,kenhys/groonga,kenhys/groonga,naoa/groonga,groonga/groonga,naoa/groonga,naoa/groonga,komainu8/groonga,kenhys/groonga,komainu8/groonga,kenhys/groonga,naoa/groonga,groonga/groonga,naoa/groonga,kenhys/groonga,kenhys/groonga,groonga/groonga,kenhys/groonga,groonga/groonga,naoa/groonga,komainu8/groonga,komainu8/groonga,groonga/groonga,komainu8/groonga