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=ahaas@chromium.org

Bug: v8:6837
Change-Id: Ic8966dfeacf02b2684eeef23fde99ec2be4ed81e
Reviewed-on: https://chromium-review.googlesource.com/671364
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48080}