Migrate from base::MakeUnique to std::make_unique.

base::MakeUnique is being deprecated as we can now use std::make_unique
when compiling code in the C++14 mode.

BUG=chromium:769107
TEST=Run unit tests.

Change-Id: If089511f90627af68fdb895be7ef079d059dbca3
Reviewed-on: https://chromium-review.googlesource.com/734423
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Andrey Pronin <apronin@chromium.org>
5 files changed