Revert "Keep a canonical list of shared function infos."

Revert "Keep a canonical list of shared function infos."

Speculative revert in the hopes of fixing serializer crashes seen in canary.

This reverts commit c1669450834436508e0007885eb7ac266cbcf083, as well as
followup change "Do not look for existing shared function info when compiling a new script."
(commit 7c43967bb73783b46c2ccf9cdd0fa716b74ce278).

BUG=chromium:503552,v8:4132
TBR=yangguo@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/1207583002

Cr-Commit-Position: refs/heads/master@{#29241}