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- Adds support for large objects
- Adds tests for strong and weak backing stores

With these changes, the marking verifier is able to catch any object
resurrections during pre-finalization as well.

Bug: 976703
Change-Id: I75097a0a0d79e136992b07d8881e9136f1a9bd4b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1669932
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#671537}