With the current attempt, trying to iterate a const ZoneChunkList doesn't even
compile. See the bug for more info.

R=marja@chromium.org

Bug: v8:6473
Change-Id: I8de7e887398be7ba5da14dc540dd40b30df2c3fe
Reviewed-on: https://chromium-review.googlesource.com/868332Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50675}