GitLab

- Define PlatformSharedMemoryRegion::PlatformHandle to use the typed
  zx::unowned_vmo wrapper, rather than raw zx_handle_t.
- Migrate zx_vmar_* call-sites off of *_old() variants, to use zx::vmar
  methods.

Change-Id: Iade0c388c7f593303ad79d2504e438e88ab2807f
Reviewed-on: https://chromium-review.googlesource.com/1199610Reviewed-by: Alexandr Ilin <alexilin@chromium.org>
Reviewed-by: Will Harris <wfh@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588603}