GWP-ASan: Fix copy-and-paste bug

Change this DCHECK to use the maximum appropriate size of the metadata
array instead of the slots array.

Change-Id: I78935a37a7e6555a60cd55c9c21c6bd9b6d45db0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1584987
Auto-Submit: Vlad Tsyrklevich <vtsyrklevich@chromium.org>
Reviewed-by: Vitaly Buka <vitalybuka@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654230}
1 file changed