They were already implemented mostly in C++ (only error/negative
cases were handled in script), so this is mostly just a cleanup.
Only the constructors remain in script after this CL.

Bug: v8:6354
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I5b3579337a8e33dc30d49c2da5cfd42baec697bb
Reviewed-on: https://chromium-review.googlesource.com/531670Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45924}