The tagging logic used for serializing and deserializing WasmCode
objects is by now only used in the "wasm-serialization.cc" unit.

R=clemensh@chromium.org

Change-Id: I31bd82e7dbd17f713c5e51073dfd9836f1ddaed7
Reviewed-on: https://chromium-review.googlesource.com/975303Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52140}