Remove serializer-specific hash table size heuristic.

Remove serializer-specific hash table size heuristic.

The heuristic can cause weird behavior when bootstrapping.
The memory savings is not worth this hassle.

Committed: https://crrev.com/fc80f29a582b758d14aae864232624ca45e47ddc
Cr-Commit-Position: refs/heads/master@{#30019}

Review URL: https://codereview.chromium.org/1265983006

Cr-Commit-Position: refs/heads/master@{#30026}