Removes some unused functions in ParseInfo and makes the associated fields unique_ptr instead
of shared_ptr. Also removes an unused zone in Compiler.

Change-Id: Idf1fbfb523cfc2b9a265d2855b1167770203cfd5
Reviewed-on: https://chromium-review.googlesource.com/1185193
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55342}