For such a simple predicate, calling a(n inline) function that checks against
the values is faster (*) than maintaining the cache.

(*) When scanning a file that contains only comments, we're basically calling
IsLineTerminator in a loop. Parsing such files is now 7-18% faster in local
experiments.

BUG=v8:6092

Change-Id: I6a8f2aba9669a76152292f4e6c7853638d15aae3
Reviewed-on: https://chromium-review.googlesource.com/645633
Commit-Queue: Marja Hölttä <marja@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47810}