Code comments are heap-allocated and never freed. We don't want to
attach them to the code object via a finalizer, since that could change
gc timing and heap layout when you enable code comments. They are used
to testing only anyway, so leaking is acceptable here.

R=bmeurer@chromium.org, jarin@chromium.org

Bug: v8:7738
Change-Id: I27b0f95db1d66b57f4f113c154f23edb84e6700d
Reviewed-on: https://chromium-review.googlesource.com/1051241
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53107}