GitLab

https://crrev.com/675319 added more std::unique_ptr usage, but did not
always #include <memory>. As a result, the CL only builds due to luck.
When one sets use_custom_cxx=false, they no longer build, as seen in
this thread:
https://groups.google.com/a/chromium.org/d/topic/chromium-packagers/UyJsVJ5QqWo/discussion

Change-Id: Ib9812b3210dac60176128b22c3881f7f33d785f8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1713037Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#679819}