Now that the preparser doesn't track errors anymore, it also doesn't make sense
to prepare the message.

Change-Id: Ifc69e67f9220be69812257b0fc18b55097236dbd
Reviewed-on: https://chromium-review.googlesource.com/c/1275818
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56574}