One step closer to the informally-agreed upon specification
that structured cloning will always succeed, meaning, if
we fail to deserialize (e.g. because version mismatch in
serialized format and v8 version), we recompile.

As part of this work, the deserializer will need to become
more resilient to invalid input data, and fail graciously
rather than CHECK-ing. This CL addresses some of that,
sufficient to unblock the current serialization tests.
Subsequent CLs will add more testing and the appropriate
fixes.

BUG=639090

Review-Url: https://codereview.chromium.org/2395793003
Cr-Commit-Position: refs/heads/master@{#40058}