Convert //base to use std::unique_ptr With bonus IWYU fixes that weren't caught by local android gn, cros gn, linux gn, mac gyp, and win gyp builds. BUG=554298 TBR=brettw@chromium.org Review URL: https://codereview.chromium.org/1852433005 Cr-Original-Commit-Position: refs/heads/master@{#385011} Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src Cr-Mirrored-Commit: 093de9b30c0ba6ded896506a297314e5ed818b89