This is a reland of ca086a49

Original change's description:
> [parser] Perfect hash for keywords
> 
> Use gperf to generate a perfect hash table for keyword lookup. Adds a
> python script which munges the output of gperf and adds additional
> cleanup and optimisations.
> 
> Change-Id: I3656a7287dbd0688917893de3a671faef9e4578a
> Reviewed-on: https://chromium-review.googlesource.com/c/1349240
> Commit-Queue: Leszek Swirski <leszeks@chromium.org>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Reviewed-by: Marja Hölttä <marja@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#57790}

Change-Id: Ifb53527ba3d0652ea4f5d03740f7c856ad5d91da
Reviewed-on: https://chromium-review.googlesource.com/c/1350121Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57831}