Small readability increase for the keyword check magic, using memcmp
instead of a chain of raw comparisons. Could allow better codegen for
memcmp-aware compilers, though in practice seems to have little effect
on generated code.

Change-Id: I91020fe67cebc9270c61c4c678e15217e436afff
Reviewed-on: https://chromium-review.googlesource.com/c/1340291Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57595}