Use the (D)CHECK_{EQ,NE,GT,...} macros instead of (D)CHECK with an
embedded comparison. This gives better error messages and also does the
right comparison for signed/unsigned mismatches.

This will allow us to reenable the readability/check cpplint check.

R=yangguo@chromium.org

Bug: v8:6837
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I88e5afea1ad0fdf23a81b380e64ff356bbc20112
Reviewed-on: https://chromium-review.googlesource.com/681374Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48138}