While this seems like it should be true, the array buffer is not actually
neutered until the end of cloning. This is so that, if an exception is thrown
during serialization, the original array buffer is not left neutered. As a
result, Blink will not have neutered the buffer.

This fixes some DCHECK failures during layout tests.

BUG=chromium:148757

Review-Url: https://codereview.chromium.org/2466563002
Cr-Commit-Position: refs/heads/master@{#40675}