This helps debugging incorrect usage of the SnapshotCreator API in
debug mode.

Change-Id: Ibd9db76a5f460cdf7ea6d14e865592ebaf69aeef
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1648240Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62095}