and non-recursive in order to let Clang inline it.
Bonus: Drop IsTwoByteRepresentationUnderneath, which was dead code
except for one test, and is semantically redundant.

Bug: chromium:910573
Change-Id: I86f1c312e93ab875b4b42101ac65ddc94b1c9518
Reviewed-on: https://chromium-review.googlesource.com/c/1369086Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58171}