Revert of [serializer] print use count of external references. (patchset #2 id:20001 of https://codereview.chromium.org/2495213003/ )

Reason for revert:
Breaks https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20vtunejit/builds/14690 compile

Original issue's description:
> [serializer] print use count of external references.
>
> R=peria@chromium.org, vogelheim@chromium.org
> BUG=chromium:617892
> NOPRESUBMIT=true

TBR=peria@chromium.org,vogelheim@chromium.org,yangguo@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:617892

Review-Url: https://codereview.chromium.org/2498163003
Cr-Commit-Position: refs/heads/master@{#40980}