Because the preprocessor is used independently from the compiler,
we need a way to track max token size when we don't have access
to the parse context with the current spec.

BUG=angle:550

Change-Id: Idf5035ec2c001ee75f264151ab3c4e92f3cd44d7
Reviewed-on: https://chromium-review.googlesource.com/187140Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Reviewed-by: Nicolas Capens <nicolascapens@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>