On x64, we optimize out EmbeddedReferences, unless we explicitly
indicate serialization is enabled. We serialize js-to-wasm wrappers,
which include such references.

Bug: v8:7083
Change-Id: I976da4af74bf7ee3245e1465b8e47f2c042ec3b4
Reviewed-on: https://chromium-review.googlesource.com/780207Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Reviewed-by: Eric Holk <eholk@chromium.org>
Commit-Queue: Mircea Trofin <mtrofin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49546}