- Moves leak sanitizer code to callers of OS:: Memory functions.
- Changes signature of OS::ReleasePartialRegion to be more generic,
  removing the parameters that only make sense as part of VirtualMemory.

Bug: chromium:756050
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I2f1401c9b0856b2eaf36b80b5f141e935ef63e1c
Reviewed-on: https://chromium-review.googlesource.com/685741Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48250}