GitLab

Change the class hierarchy used in this test in order to
eliminate two static_casts that are invalid under CFI.

While here, change the tests to use std::unique_ptr in order
to simplify memory management (and fix a memory leak).

Bug: 507755
Change-Id: Ibb077fee1f4286d46c9da3fbe0ce296f30e11c96
Reviewed-on: https://chromium-review.googlesource.com/818531Reviewed-by: Will Harris <wfh@chromium.org>
Commit-Queue: Peter Collingbourne <pcc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523649}