Fixes a crash found by clusterfuzz caused by a call to
std::vector::reserve with a huge capacity, and reverts to ZoneList
handling as a tentative fix for performance regressions on the slow
@@replace path.

BUG=chromium:707187,chromium:706748,v8:5437

Review-Url: https://codereview.chromium.org/2787343002
Cr-Commit-Position: refs/heads/master@{#44311}