Revert of Fix bug when transferring SharedArrayBuffer to multiple Workers. (patchset #3 id:40001 of https://codereview.chromium.org/1215233004/)

Reason for revert:
[Sheriff] Test hangs sometimes and times out flakily. E.g.: http://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20nosse3/builds/4551/steps/Check%20%28flakes%29/logs/d8-worker-sharedarray..

Original issue's description:
> Fix bug when transferring SharedArrayBuffer to multiple Workers.
>
> Previously, the serialization code would call Externalize for every transferred
> ArrayBuffer or SharedArrayBuffer, but that function can only be called once. If
> the buffer is already externalized, we should call GetContents instead.
>
> Also fix use-after-free bug when transferring ArrayBuffers. The transferred
> ArrayBuffer must be internalized in the new isolate, or be managed by the
> Shell. The current code gives it to the isolate externalized and frees it
> immediately afterward when the SerializationData object is destroyed.
>
> BUG=chromium:497295
> R=jarin@chromium.org
> LOG=n
>
> Committed: https://crrev.com/dd7962bf7838f8379ba776ee6b7b0e4d3bec2140
> Cr-Commit-Position: refs/heads/master@{#29499}

TBR=jarin@chromium.org,jochen@chromium.org,binji@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:497295

Review URL: https://codereview.chromium.org/1224843008

Cr-Commit-Position: refs/heads/master@{#29506}