Currently when memory size references are updated with zero initial memory during GrowMemory/Relocation of Instance objects, the bounds check does not take into account the size of memtype.

R=titzer@chromium.org, bradnelson@chromium.org

Review-Url: https://codereview.chromium.org/2416543002
Cr-Commit-Position: refs/heads/master@{#40326}