This reverts commit 5bbd1921.

Reason for revert: Tentative revert for crbug.com/879988

TBR=sattlerf@chromium.org,verwaest@chromium.org

Original change's description:
> [scanner] Inlining ScanIdentifier and Token check
>
> This improves parse time for code-load and other benchmarks.
>
> Bug: v8:7926
> Change-Id: I9c8017f2e7f73dd952c025db5abe8e4062e6ef9b
> Reviewed-on: https://chromium-review.googlesource.com/1196506
> Commit-Queue: Florian Sattler <sattlerf@google.com>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#55521}

TBR=marja@chromium.org,verwaest@chromium.org,sattlerf@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: v8:7926, chromium:879988
Change-Id: Ic71d9cf63b69c0f9560851259f434b02cc082417
Reviewed-on: https://chromium-review.googlesource.com/1202086
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55592}