Fix PartitionAlloc cookies for small in-place reallocs.

BUG=781473

Change-Id: I45866a704b5b112804cb478260c0a5273597cf5f
Reviewed-on: https://chromium-review.googlesource.com/756179
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#514411}
2 files changed